Frist off, get into the habbit of dropping into the shops during the week, so you don't have to contend with the crazies who congregate on the weekends.

Play something on its own (no amp). If it sounds good like this, you will probably like it even better after you plug it in. It has to FEEL right. Ideally, the instrument is an extension of your self. You shouldn't have to rearrange yourself to suit the guitar.

When you do plug in, start with the amp set for a clean sound. Get to know what the GUITAR sounds like. For the versatility you need, you should check out something with at least two humbuckers that have switches for selecting series or parallel coil arrangement, and phasing. That hollow sound you can get from your comfortable old Squier can be approximated with a humbucker axe set for series, out-of-phase connection.

Don't make any decisions in a hurry. Don't let some string-slingin' showoff who works at the store give you any guff. It's your money, your music, and your choice.