Line Conditioner or New Power Cords?

That depends a lot on your power source and how bad it might be. I put 3 Cardas Golden Reference power cords on my Arcam AVP700/P1000/DV79 and Merlin TSM-MX's with very good results, making a very smooth and tonally neutral combo even smoother. Especially notable was dialog for movies which became even better defined (with phantom center). Video was about the same as far as I could tell. On a'gon, CGR PC's are actually pretty reasonably priced relative to many cords.

When I inserted a Sound Application Reference LineStage power conditioner from my 2-channel system briefly, I wish I hadn't because I can't really afford a second one. The video was much cleaner and dynamics were improved for audio. The background seemed blacker causing dynamic changes (quiet to loud) to be much more distinct. I just couldn't justify the cost, so I'd say, at least in my case, the power cords came first but were definitely worth it. A power filter with lousy cords is still going to sound rather lousy, so I'd probably go with the cords.

Everyone has an opinion on power conditioning and I'm sure each system and power situation presents a unique problem to solve. For my part, $50 an outlet from Sound Applications for my dedicated circuits (2) was a no brainer first step. Very easy to do and had a significant impact. Next were the cords (not cheap or midprice though). Again a very noticable difference, mostly on what I'd call the "signal" or sounds being made. Nothing was taken away in terms of music. Lastly with power conditioners, I had a chance to try a small number of these (not enough). Almost every one balanced or not seemed to take away more than the "noise", as in music. The ONLY one I tried that took away the "noise" by making it a more silent background, and didn't harm the music at all was the Sound Application RLS filter. It is ridiculously expensive, but it sounds great and gives me peace of mind that I've done all I can in that area. It also allows me to "tune" quite a bit with cords, quite often requiring less exotic species. Jim Weil (Sound App guru) actually recommended a <$50 Belden stock cord out of the Newark Electronics catalog to me. Haven't dipped that low just yet, but it's tempting to get a little of that capital spent on power cords back in the till for other goodies.