I've used lots of cables with the three Supratek preamps I've owned and I'll get into that below. The issues you mention - particularly the "boomy bass" can be resolved with better tubes. I suggest as a low budget solution, removing the Sovetek 5881's and replacing with Sylvania 6F6 - on the high end some Western Electric or National Union 350B's will help to tighten things up. The rectifier for these tubes which *I* have found to be superior is the Bendix 6106. They're about 30 bucks each. Buy a couple because results vary and they have a weird break in. I almost tossed mine out the window in the first week but after a few months, its #1 no matter what I compare to.
Next & unfortunately, given the high-gain nature of the Chardonnay, there is no cable that will remove the slight hiss/hum. You might try the $189 Ah! AC offset killer available from Upscale Audio. Information on the AC Offset Killer can be found here: http://www.upscaleaudio.com/AH!/acoffset.htm
For cables, I use Siltech Compass Lake going in and NBS Monitor 0 going out. I do not suggest you run out and buy these cables. They are just about the best cables available but at their combined retail price, one could buy 4 Supratek Cortese preamps. No joke.
Cables in most systems seem to be "evolutionary" whereas the best aren't just purchased outright, they are worked up to... The best solution is to keep cycling cables until you reach the point where your budget and tastes are either satisfied or exhausted... which-ever comes first.
I have used the OTA, the TMC (yellow / white) and the Audience AU24, and my personal feelings about these cables should not be discussed in public forums. That said, what these cables do provide is a good entry point to the adventure of finding the right cables for you.
I'd suggest a TMC (yellow or white doesn't matter) in and Audience AU24 out. The AU24's are quite rolled off on top and a bit wooly sounding everywhere else. The TMC's are detailed, savagely unrefined, slightly edgy, tarnish when you touch the connectors and a pain to use - because of their stiffness. Together (and with the Supratek in-between) they may be a match made in heaven - for the price.
That is if they do what I suspect they might by canceling out the others flaws.
The OTA was in my system for a few months when it was new to the market. I fell for the hype and purchased it. Let me tell you... I've never heard a cable that sucked the life out of music like the OTA.
There are so many great cables out there but I know quite a few supratek owners who've settled on:
Audio Note (AN-Vz or KSL-LP1) in
NBS (Professional and/or Statement) out
This is not exactly a cheap solution but it's a good one to work toward. Audio Note AN-Vx and NBS Master would be a good choice for less money. Dropping to models below these cables defeats the benefits of the brands altogether and there are better values at those prices.
I hope this helps.