Addressing your question about the speakers: A member just ordered the Fiero Store replacements. They are 4 ohm. The rear speakers are 2-way, while the front are standard speakers. Didn't check to see if the power rating was listed.
I ordererd speakers from onlinecarstereo.com and after 3 months, they still hadn't shipped. Seemed like speakers less expensive than mine were all out of stock, and they wouldn't give any compensation for the long wait, like free shipping, so I had to order another more expensive pair. 120 Watt, but everything they had was 4 ohm. Couldn't find 10 ohm speakers anywhere.
Onlinecarstereo.com does have a good pair of 4 x 10 Pioneers for about $79, and that's about $20 cheaper than I've found them anywhere else.