What are you trying to gain over your current setup? Two 10" drivers are usually different than a single 12". Two tens will be louder than you currently have, but a single 12" will play the lower frequencies louder. What size box are you willing to have?
Here are some options:
Dayton DSQ 12"
Dayton DVC 12"
Dayton Titantic 12"
Adire Audio Shiva (12")
Blueprint 1202 or two 1001's
Stryke has a pre-order on the AV12 or $140 which is the best deal
Lambda Acoustics has some B-stock PB drivers for $150, a single PB15 will more than make you happy for $150, but it needs a larger box.
