Best value power amp with output level controls.

Over the years, my former "high end" audio system has dissipated somewhat. Remaining, however, are a Melos Sha-Gold preamplifier and a Parasound D/AC 1600 HDCD DAC. I currently utilizing the Melos exclusively as a headphone amplifier only. I wish to purchase a power amp with output level controls (as the photentiometer in the Melos seems not to be operating properly) so to fully realize the potentential of the SHA-Gold. My price range is $300.00 and below. In Audiogon, I have seen and am interested in the following; Parasound HCA-800 II; Hafler P-1500; and Hafler 9130. As far as new units are concerned, the Audio Source Amp 200 is intriqueing. My speakers are a pair of Infinity Alpha 10's and my subwoofer is Velodyne 1215X. My musical tastes are "light rock" and hard pop", if that makes any sense. Any and all comments and advice are most welcomed.
I don't know about "best" but Adcom made something that you could probably find here in that price range (???L?).
Describe the issue with your volume pot. If it's just noisey or seems to fluctuate up and down while being adjusted, it might just need a cleaning. You could do it yourself very easily with can of television tuner cleaner, available at any Radio Shack. It's as simple as removing the knob, spraying some into the pot at the base and twisting the knob back and forth a few times. Might take more than one application. In the end, you'll have a fully functional pre again. That's a good one worth saving.

The afore mentioned Adcom was the GFA-535L and is a great suggestion. Quite musical compared to the other Adcom amps of it's vintage.
A local technician can easily replace a worn-out potentiometer if Creeper's cleaning suggestion doesn't work. Personally, I've never had any luck rehabbing pots with tuner cleaner - all the ones I've tried this with were physically worn out as opposed to simply corroded or dirty. It's well worth a shot though.

B&K also has made power amps with output controls that may fall into your pricerange or a little above - also check out Parasound as you've mentioned.

In most cases however, the volume controls on a power amp are going to be up back by the amp's inputs and outputs - that may present a usability problem. I'd also guess that these typically smaller volume controls are not going to be as robust as a volume control designed for more frequent use - they may wear out rather quickly with regular use.
The Sony ES series power amps had level controls and worked nicely. I think the TA-N55ES, at 110 watts, is not a bad choice in your price range. I owned a couple of these amps and found them to be very revealing, sometimes a tad bright maybe. I preferred them to Adcom. Good luck.