I've decided to focus my energy on my car, the Volvo 850. First, to get it working, just bought an ECU on ebay for $50. Its used, but tested working and guaranteed for 30 days.
Next will come some modifications to the stereo. I'm not going to bother with subwoofers, or changing the receiver for that matter.The stock receiver has a multichannel amplifier out, so I'll buy a good quality amp and hook it up between the head unit and the car's new speakers, which I will install. The car came with a 10 disc CD changer in the trunk, so that won't be a problem.
Next, would probably come some performance upgrades. Its already really good at 222 horsepower, but I'd like to up that. New air intake, and maybe a more powerful turbo.
Lastly, cosmetic modifications will take place. Probably a wood grain dash kit, just to give it that luxury car look. A (stock, OEM) spoiler, and new, chrome rims. Still thinking about a body kit, but $800 is a lot to throw down for a few pieces of plastic. Will probably not bother with it. I really think I could make this car really nice, not that it isn't nice as is, but I want to truly make it unique. I want to make it mine.