If you are worried about what router to buy you probably aren't ready to start building your guitar bodies yet. I'm surprise that six pages into replies to your question that no one has pointed out that what router choice you make is not an important initial consideration.
What you need most of all is a solid
workbench.
Anyone who has successfully built a wood project will tell you that the most important thing to get right is your joints. To get the joints right the wood MUST BE true and square. You aren't going to find quality pieces of wood at the box hardware store in the mall parking lot (i.e., Home Depot or Lowes). They don't tend to carry
mahogany or flame maple or whatever base wood you will want to build a guitar from. You are going to be buying 4/4 and 6/4 lumber from a hardware specialist. This requires a bit of mill work to make it usable.
You need a jointer to make truly square plained edges to properly glue pieces together. Trying to glue together slabs that have not been plained to true will ensure that your guitar bodies fail and warp. True and square is a fundamental of good woodworking and separates it from crap. This needs to be done shortly before gluing and clamping before the wood decides to change shape. Once you have your body glued together you will need to surface plain it to the correct depth. Remember, this is rough wood that you are working with and you are going to need to mill about 1/4 inch off of each side of the body. You will probably want a surface plainer for this (could be done by hand by
an expert with nothing better to do with his life).
Clamps. You can never have enough clamps. I paid way more for my clamps than I did for any of my routers.
Router bits (which will determine what collet size your router needs to have). You are going to spend more for your router bits than you are for your router. If any of your bits are more than about an inch in diameter you will want to make sure that your router has variable speed and a soft start. Once you get to 2 inch diameter bits don't even think about using it in a router without variable speed.
I'm not trying to discourage you. You may be able to make friends with someone who has access to a good jointer and a large enough surface plainer to mill a guitar body. This might also be a good source for some additional information on choosing other tools (biscuit cutters, band saws, etc.)
Glen