You should check out Harmonic Technology's gear. We seem to have similar tastes in music and sonics. I recently went all the way with HT, replacing much more expensive Transparent cables throughout. Good luck.
I am also strongly value-oriented when it comes to audio gear, so I'm not sure that I'd recommend adding new power cords at this stage in your system. However, if you want to look at this anyway, then check out HCM Audio (www.hcmaudio.com). They have been running a clearance sale on several brands of power cords, including AudioQuest. I bought AudioQuest power cords from HCM to replace the stock cords on my Bryston amps and pre/pro, and found HCM's price and service to be very good.
Interconnects are a different matter. Upgrading your interconnects is much more likely to yield audible improvements to your system. I have used a number of lower and mid-priced interconnects in my system, and have recently settled on Super Silver interconnects from HomeGrownAudio (I am using 7 pair in my current audio setup). You can buy kits for HGA's interconnects -- the kit for the 1 meter Super Silver, for example, sells for $59. All you need to assemble the Super Silver interconnect is a soldering pen, electrical circuit tester, the ability to follow directions, and a bit of skill.
It wasn't clear from your post if you also wanted advice on speaker cables. If you do, then I can make no better recommendation than Kimber Kable 4TC or 8TC. This cable is certainly one of the best products at (or anywhere near) its price range, and has even been recommended by The Absolute Sound for use in quite expensive systems. I have been using Kimber products for years, and think their moderately priced interconnects and speaker cable are genuine high value products.
Cant go wrong with Kimber Kable for your interconnect needs and speaker cables too.Bang for the buck.I use the PBJ interconnects in my H.T.system as I try to keep the costs at a reasonable threshold without breaking the bank,and if you want to go a bit better,try the silver streak,or get the KCAG used.Cheers and good luck.
Your tastes, sonically speaking, seem to be similar to my own. I'm also using a Belles HR 150a a tubed pre, and Kimber 4tc. Kimber is a great value, whether 4 or 8 tc. I recently bought Analysis Plus Oval 9 and now use the Kimber & the A+ Oval 9 in a biwire combination. The suggestion to check out DIY cable for power cords & interconnects is also a good idea for someone seeking value. I've experimented with both Bob Crump's and Chris Venhaus' diy power cord recipes. With the Belles amp, Venhaus' "flavor 2" power cord constructed from Belden 83802 teflon jacketed wire sounded the best of all diy cords I've tried. If interested, go to www.geocities.com/venhaus1/diymains.html. I've also had very good success with the Music Metre interconnect cables that are auctioned here on Audiogon for a reasonable price.
I'm using HomeGrown cables as well (2 pairs, along with Nordost and MIT cables) and while I wouldn't characterize the HG SuperSilver as "reference quality", they're excellent cables at very attractive price. The same could be said for the Nordost Blue Heavens and MIT's that I'm using in other parts of the system, although they tend to run a bit more, and have very different characteristics (which in their current configuration works very well).
There's a lot to be said for building your own cables as well. While this isn't exactly what the neophyte necessarily wants to get involved with when first setting up a system, but its a good way of getting excellent cables for very little money. I second the suggestion of looking at www.diycable.com and giving one their cables a whirl. All of the recipes they offer are well traveled and very well respected, so its hard to think that you'd go too far wrong. If you ever get seriously interested in DIY cable projects, there are a number of recipes and vendors out there that you can avail yourself of.
One thing to keep in mind is that cables are as much a part of the system as any of the electronics in so much as they impart their own characteristics to the sound (they're not supposed to, but in reality they do). Some experimentation will likely be required to find the very best match for your components and tastes, and as such I'd advise starting off on the low end (price-wise) and giving yourself an opportunity to play around a bit without breaking the bank. There are *many* used cables available here on Agon, so its a pretty good place to start shopping.
I've posted it before, but you really need to try-before-you -buy. Shopping by brand and/or price can be a costly and/or frustrating proposition. I have always rented cables from The Cable Company (1-800-FAT-WYRE) to try them in my system before purchasing. They rent them for, like, 5% of the retail price and all rental fees go towards purchase, so you really have nothing to lose. They also carry virtually all brands of cable, so you can try a wide range of brands and prices (even some of the insanely-priced "exotics"), to get a feel for which ones match well with your system/room/musical tastes and what trade offs you are making by choosing one over the other. Definitely the way to go.