listening is good... but its still hard to tell... in the store, the speakers are usually in individual, sealed boxes... probably hooked up to an amp... so the sound is totally different as if they were in the car.

As far as I know, the 90-93 EX and SE had 5's in the front (not 5 1/4's, just 5" speakers).

The Alpine's will provide slightly fuller bass... the infinitys will be a little "tighter".

Polks have excelent bass response... i'd say you heard wrong. Polk Audio is my second choice for car audio, first for home audio... I only second polk in car audio because I can get great deals on Boston Acoustics... which also sound very, very nice.

Keep in mind, these are relatively small speakers... you're not going to get a ton of bass from them... but most 6x9's do provide pretty reasonable bass, just nothing that will match a subwoofer.

Out of your choices, i'd say go for the alpines... just be sure to check into what size your front speakers are... they did vary... I have seen one EX with 6.5's up front.