Any Car Audio Gurus Out There?

[rawfuls]

I have a silly old 2001 KIA Sportage... the stock speakers are absolute awful... and there's only two speakers (Passenger Door & Driver Door), so replacing both shouldn't be as expensive as I've thought. (Oh yeah, I have some in the trunk, two).

Since this would be pretty budgetary, any quick suggestions?
I'd like to just replace the speakers alone, and not complicate things with a new amp..

I just want a bit more bass and some more highs...
I'm not going for any audio competitions, just want some more to make it not sound like I'm listening to scratch...

Obviously, keeping a stock amp would be pretty limiting, but I think that's fine.
I have a rather new radio deck..