Would it be that difficult to cut out the 5x7 hole for the rear speakers so I can put some 6x9 speakers back there? Could I just draw a template and use a grinder? Thanks in advance for any input.

Well,I did that in my first 90 Supercoupe and while it sounded better, it isnt any better than the enclosed JBL woofer and tweeter. I dont think it had premium sound let alone JBL. The best upgrade I have found is a 10" cannon woofer and 150-300 watt amp.

I am gonna be using an Alpine-4.150 PDX amp for the cabin speakers. The amp will be pushing 150 watts RMS. The only thing that I can find that will be able to fit in the stock hole and handle that power is a $500+ set of speakers. I can find 6x9's to handle that power at around $100. I have an elipse 12 inch 8122 DVC sub powered by an Alpine PDX-1.600 for the rear.

you could always go round and use these (i did work great)
http://www.mjmautoinnovations.com/

go with the 6" round speakers

I went with 6.5" rounds in my 94... Front and back.

I was working with Jibit on building a sub system before he die..

I'd ask Chicken for help but he'd just put more weight in my Gen I to attempt to give himself a better edge.. LOL

You could go either way. Round speakers will give you better performance in the long run. They will get louder with alot less distortion. You should go to a car audio speciality shop and get you some baffles for your speakers. Should be able to buy them pretty reasonable. Will give you alot more midbass.