I have a single 15" and, at least to me, it's loud as hell...and clean. Glad to hear you came to your senses //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif More is not always better.
If you're really on a budget you can search around here and the other audio forums for a used amp.
You'll need to read up in the amp section on how to set your amp's gain by DMM, since you'll have two different amps and you'll want them to give about the same power to each sub.