2.1 Channel Preamplifier?

Wondering if anybody has built a 2.1 Channel preamplifier - I've seen the boards floating around on ebay but not sure if they're any good.

I'm guessing your need a series of filters to separate hf/lf, summing amplifier to combine l/r channels for subwoofer output then a few basic controls (level, etc). There was a kit I saw in the UK using 6x OPA2134's but they only sell as a completed product now.

Thoughts? It's to go into a Gainclone chassis which has regulated +/- 15v
I ended up with a KMTech 24db/octave Stereo + Sub crossover, which I am running as a pre-amplifier of sorts. It arrived in under a week, which is phenomenal postage speed.

While adjustable gain would be nice (there are onboard trimpots which I could make external, I guess), I'll just wire up with a dual-attenuator in front and use the trimpots to ensure left/right channel output is even.

Mains are high passed at 60Hz with matched to 0.5% metal film resistors (I remember reading **** gets weird if you use multiple level filters with unmatched components) and CAPY polypropylenes, sub is low passed at 100Hz with same components - some extra's from building tube amplifiers back in the day. I'm sure it won't really sound any different, but I used some low ESR electro's for decoupling with a +/-12v regulated supply. I also read about changing out IC's, but I honestly don't think I can tell the difference.

Yet to wire it all into the chassis, but it seems like a good bit of kit.