That sx1250.1 is underated. It will easily put out around 1400 watts. I think the Ava is like 800watts. I wouldn't do it. Get another avalanche, and a zx1500.1, or get a smaller amp. it could prob handle a MB Quart Raa 1000. I would give it a kicker ZX750.1 tho.
so whats wrong with what you have now? oh the amp it has to many watts for the sub? not a problem just turn the gain down and youwill be fine. all my amps are twice as strong as the rating on the speakers . why ? for peaks. rms is continus rating but not a peak rating so dont worry bout it. just watch the gain.. i see no poiunt in buying a LOWER powered amp just because the speakers are rated lower.. such a waste .... just my 2 cents tho