Guide to getting and playing better gigs
Rack Systems
Rack systems are widely regarded as the prime setup for the professional studio or touring guitarist. In the studio world, having stereo effects and the choice of direct or miked recording (or both) at your disposal are expected by some producers. It's also important to know that possessing the ability to call up several dozen preset "patches" and finding the appropriate one without slowing the pace of the session will get you called back. For the touring pro, the rack itself serves as a sturdy road case. Plus having all your components plugged in, wired together, and ready to go cuts down on setup time (and saves wear and tear on cables and jacks). Also of note, a stereo speaker setup allows you to spread your sound out on a big stage for maximum "coverage" without having to crank up the volume. Lastly, MIDI control over all your devices is a nice way to keep the "tap dancing" to a minimum.
The disadvantage of racks, of course, is price. Therefore, it's in the best interest of the guitarist to keep "trial and error" costs to a minimum. For starters, let's assume you've settled on a guitar or two that you like. Unless you enjoy hauling a truckload of axes to every gig (and keeping 'em all strung), one beauty of a rack system is that you can limit yourself to one or two guitars and still get a variety of tones. The important thing is to always take your guitar to the shop when trying out rack gear. Second, it's important to note that what you're buying is a SYSTEM. In other words, keep in mind that "chain is only as strong as its weakest link" saying and apply it to your purchases. Skimping on even one component will make your whole system sound bad.
A common mistake many players make is to prioritize the effects processor over everything else. After all, people typically associate rack systems with processed sounds. Worse yet, many people fall victim to the hype over all the super fancy "preamp/processors" out there. It's crucial to know that when you jam all that stuff into one box, there are going to be compromises. At first, it's a good idea to forget about the effects and focus on a good core tone. This means primarily choosing a killer DEDICATED preamp, but also a power amp and speaker configuration that brings out the best in the aforementioned preamp. The only way to do this is to take your guitar to a shop and experiment with various combinations. This might annoy the shop employees, but just remind them how much money you're prepared to blow if you find something you like.
As far as tones are concerned, the (preferably tube) preamp should AT LEAST have one sparkly/bouncy clean tone, one dynamic/sensitive crunch sound and one liquid/expressive lead tone. If it has a few more, great. If it only has one or two out of the three, move on. Assuming the preamp meets your tonal requirements, MIDI control, XLR "recording outputs," and a stereo effects loop with adjustable input and output levels are must-have features. The stereo power amp should have plenty of headroom, a healthy amount of power and a thick, full sound. Some power amps sound thin, therefore ruining an otherwise kickin' preamp. Using the same preamp, experiment with how different power amps affect your sound. Typically, all-tube units sound better, but various solid-state versions can be less expensive, more powerful, very reliable and may come close to achieving a tube-like tone. Let your ears be the judge on this one.
Regardless of what speaker configuration you want, opt for a good "marine-grade" plywood cabinet (avoid particleboard). Also, two cabinets set in stereo typically sound better than one cabinet wired for stereo. In terms of versatility and portability, try a system of two 1x12" cabinets: one with a closed back and one with an open back. Lastly, sample as many different brand speakers as possible through the system.
Now that you have a good core tone, it's finally time to find that effects processor. Many dedicated "guitar processors" have really cool sounds typically not found on other units. Among these are Leslie simulators, intelligent pitch shifting and "whammy" type effects. Unfortunately, many of these units also have "preamp" sections. These preamp sections can potentially cause compatibility issues with your preamp's effects loop. Bypass these sections if the option is allowed, or at least set the unit's preamp EQ as flat as humanly possible. Since you already have a great tone going, you want minimum tonal coloration from the external processing. You just want effects. When choosing a MIDI foot controller, select the unit that works best with the effects processor you've selected (the preamp is only relying on MIDI for patch changes). Since many processors offer the option of "expression" pedals, this is certainly a feature you will enjoy taking advantage of when choosing a foot controller.
Finally, choose a rack that is durable and protects your gear. You also want to find a nice compromise between keeping the rack small and light enough to be portable, but leaving a enough extra spaces for additional processors. Also, you definitely want to protect your investment with a rackmount power conditioner. A locking rackmount drawer is nice for storing cables, strings, etc. A rackmount tuner is a nice touch if there isn't one built in the processor. Just make sure to keep the tuner out of the signal patch when you aren't using it. Tuners can kill your tone. Now comes the finances. Other guitar setups allow you to piece stuff together as you acquire the cash. Not so here. Much like your home stereo, a rack system is the kind of thing that's useless unless you buy the whole thing at once... at least the preamp, amp and speakers. If you don't feel like waiting until you can save the cash, this is one rare instance where it's not a bad idea to take out a loan. At least you can deduct it on your taxes, right?