Really, the Samson amp that SVS sells is going to be your best combination of the mentioned qualities.
You could get a monoblock amp for cheaper than the Samson, but I think you'd be sacrificing quality for price. Plus you'd be out the option of using an extra sub (or any other speaker for that matter) in the future without buying another amp.
Also, if you shop it around, you can find the Samson for less than SVS sells for. Not a ton, but check out some pro audio sites like www.zzsounds.com or some place like that. You might can find it for up to $50 less depending on the model you choose.
**UPDATE**
I just checked the site above and the S700 is $40 less with free shipping and the S1000 is $60 less with free shipping.
They also offer a 275 watt per channel S550 for $299.95 with free shipping.
Not trying to run business away from SVS, but $$ is $$.
I was looking for a mono solution so that I could possibly cut the amp price in half. I know I'm never going to need 2 CS subs in my room, so the extra power is worthless. (Unless the CS can take the bridge power?)
I understand that....that's kind of my situation as well. I've got the older Fidek amp that SVS offered and am only using one channel of it.
When I first ordered the sub, I was frantically searching for a mono amp so I wouldn't waste a channel, but I couldn't find anything that compared in quality and performance than what SVS offered.
AudioSource has some pretty inexpensive monoblock amps that, by the specs, should do a good job with an SVS, but who knows about the quality.
I'd still look into the Samson. Granted, you'll have a channel you may never use, but I still don't think you'll be able to beat it in price.
The deal with mono amps is that not everybody offers them....mostly higher end companies, so the "cut the price in half" thinking really doesn't pan.