integrated to drive 2 15" passive subs

Any recommendations on an integrated amp to drive two passive 15" subs. I have an old 85W Yamaha that I think doesnt produce enough current to drive the subs (bass becomes loose when i start cranking up the volume past 1/2). I was thinking of the Nad C370 or a Rotel. Looking at a 100W/channel amp at the minimum and solid state. Any suggetions?
I am not sure about integrated to drive subs. What are the subs? What is the rest of your system comprised of?

Are they stand alone subs? If so, have you thought about buying a couple of plate amps from Parts Express or such and installing them in you subs? If you don't want to cut a hole in subs you could build an enclosure for the plate amp. If you don't have the tools to make the enclosures for the amps, email me and I could possible help you out.
Eldarado. The subs are DIY and have 2nd order crossovers. Have a onkyo pre/power that drive the mid/highs. I am using one of the tape outs of the pre to the yamaha to drive the subs. Dont really want to convert the subs to active.

Why don't you take a look at some of the pro amps...Parts Express and other pro gear sellers carry them. They are fairly cheap and should be good sub amps I'd guess...they don't all have fans.

thanks will browse parts express.