Am I correct in assuming that shape matters very little when running plugged in to a P.A. or Amp?
Guitar tone has so many variables... wood, shape, string construction, string tension/thickness, bracing, etc. And if you're amplifying it, you have to add the kind of pickup system you're using to the mix.
I'll give you a short rundown on wood and tone:
For the top, the most common woods used are spruce and cedar. The two most common spruce tops are Sitka or Engelmann. Engelmann will provide a little more volume, give a bright tone, and will mature (reach it's full tonal quality) quicker than Sitka. Sitka, however, is the more durable of the two and will have a slightly warmer tone. Cedar will give a warmer tone than either of the Spruces. As for cost, Engelmann will cost more than the other two.
For backs and sides there a far more options. The most common being Mahogany, Indian Rosewood, and Maple. Of the three, maple is going to be the brightest - very punchy, followed by mahogany (also on the bright side but offering a very clear tone), and then Indian Rosewood would be a warmer tone and will have more of a bass presence than the other two.
There are other woods that are becoming more common these days as luthiers try to distinguish themselves. Cocobolo, as far as tone is concerned, falls between mahogany and rosewood but it weighs a ton. There are some who feel that, tonally, cocobolo is the closest wood to Brazilian rosewood but I'm not sure that's true. I don't think it's true of my 2002 Taylor 814ce Ltd. but I haven't played enough Brazilian rosewood guitars to really know for sure. Brazilian rosewood is the warmest and most prized of the tonal woods and will probably push the cost of any guitar into the $10,000+ range these days (and that explains why I don't own one). And a wood that I'm becoming more and more a fan of is walnut. Walnut gives you tons of sustain, gives a brighter response than mahogany but without sacrificing the bass as you would with maple. Koa is also popular but I haven't played any Koa guitars so I can't offer an opinion.
Shape will have less impact on tone than wood does, but it still should be considered. Pickers and strummers tend to gravitate towards dreadnaughts and jumbos. Fingerpickers lean towards small jumbos, concert-sized, and more recently parlour guitars (which have seen renewed popularity). The parlour guitars are also very popular amongst blues players. However, shape works hand in hand with bracing and wood thickness, so that two guitars with the same shape can sound very different if the bracing is not identical and the woods are of different thicknesses.
If I were you, I'd spend a few weeks going around to as many guitar stores as you can and playing everything in your price range. Don't worry about what a guitar looks like at this point, just try to get some idea as to what tone appeals to you. The more you enjoy the sound of a guitar, the more you're going to play it. Once you zero in on the tone you like, you'll be able to narrow your choices and make a decision.
Another thing I'd stress is playability. Some guitars are well-made and have great action (the space between the fretboard and the strings). Others are crap and will always be hard to play. Wherever you wind up buying your instrument, I'd get it right to a good luthier for a setup (yes, even acoustics need to be setup). He'll also be able to alert you to any potential problems with your purchase that may not be noticeable to an untrained eye such as a warped neck.
Lastly, and this is something I've been telling people for years, buy as much guitar as you can afford. A better guitar will inspire you while a crappy guitar will always sound like a crappy guitar no matter how good the player is.
Good luck with your guitar hunt. I love guitar shopping!!!
Jim
) is to go play guitars and pick one I like. It's just good to have a starting point to know what I want to narrow my original search down to.