Time for new tires..., I still wanna keep the stock rims...unless... Options

[king_wsk]

Its been a long time since I've posted anything here. My tred is just about entirely gone on all four tires (I rotated them about 5k ago). I really don't want to break the bank right now as I'm saving up for a down on my first house... however I want more than just generic tires for my stock 15" aluminum rims (from the sports package apparently). The rims are still nice and in good condition. I currently have TOYO 205/55R15 X.

I'm basically torn between just getting a good set of BFG's with a 60,000 mile warranty (at about $400) or looking for a decent (but inexpensive) set of 17's and geting 215/__r17.... which might mean I'd need to get lowering springs.

I really don't want the car to be overall lower (net effect of the springs and tires) as I don't want to be scraping my front and rear ends (more than I already do). I'd really like the tires to perform at least 40k miles before I need to change them, and I'm on a tight budget.

Any suggestions? Think I could get a used set of 17's 7"ers (assuming 7" = 215) and then new tires? Also, by having a lower aspect ratio even with the usage of larger rims, does the net effect cancel out the overall height difference? I.E. my stock 205/55R15's == 205/40R17 as far as ground clearance?

This is my first time buying tires for this car, and would be my first set of rims should I decide to do so.