As one amplifier engineer once said, the design of amplifiers is well understood these days, so any amplifier from a major brand should work fine even if you buy it cheaply. It's amazing what you can buy even for $150-200. However, at $80-100 I'd start worrying about the issues with the basic build quality of the amplifier. E.g. did they use chewing gum instead of glue? Of course, there are exceptions sometimes, when some vendors is having a blowout of their old stock, etc.
Anyways, there is not enough information in your post. How much power do you need? Any special requirements with respect to installation details, like desired amplifier shape or wire thickness etc? Are those subwoofers dual 2ohm each or single voice coil each? This can be very important. Finally, how much power do you need? Anyways, as far as cheap amps go, if your subwoofers will be wired together for 1ohm or 2ohm, I'd recommend to take a look at MB Quart REF1. These were solid amps, but my understanding no longer made.
Sonicelectronix is selling REF1.800 for $110 which is a fair deal. If you will wire subwoofers for final 4ohm load, it's probably better to buy a 2-channel amp and bridge it. I'd suggest the discontinued Boston Acoustics GT-2125 ($110 at sonic right now) or a PPI P600.2 if you need a bit more power than BA-GT amp.