You'll want to order the amp bypass kit from Crutchfield (888) 955-6000 for $20. It's very easy (about an hour) with the kit and makes a notable improvement. It's definately worth every penny.
I'm a little puzzled by your low sub output. The Clarion has got 4V pre-outs, so you'll most likely put the gain to minimum (unless your amp handles up to 8V worth of signal) to match the signal level between the HU and amp. It could possibly be your sub requires more power than the 170w you're sending it (assuming you're bridging the amp to a mono load with a SVC 4ohm sub). It's possibe that your sub could also be in an enclosure which is poorly suited to it.
Blau's are decent speakers. Nothing outstanding, but much better than stock.
