Fullest sounding high C

I've been pleased with the results I get from D'Addario SloWounds. I think their C is an .032, which is a hair bigger than the industry standard of .030.

I always heard them as less bright than a stainless roundwound, though. The regular nickel XL series C strings are a little more zingy than SWs, but not as much as stainless.

 

I'm not playing a six now, but when I had my Peavey Axcelerator 6, LaBella Hard-Rockin' Steels were the best strings I tried. The C was pretty thick-sounding (for a C string).

 

Which set of Dean Markley's are you using?

The Medium gage has a good thick C string - I think it is .35 !
The Tension on the C in the Medium gage is quite a bit higher than the Will Lee gage.

In general, a thicker string from the same product line (from the same manufacturer) tends to sound thicker - but it also has more tension.

 

Probably not what you're looking for, but:
* TI Jazz Flats (6-string 34") seem nicely balanced (I don't like the "piano" sound of round-wounds)

* No matter the strings, maybe (er, like me) you like to crank-up the low-eq. That will make the higher notes too quiet/dead. Especially noticable on a 6-stringer. Try a more flat EQ (or boost the mids to match the lows).

* Get a (good!) compressor. I use a cheapo DigiTech "Bass Squeeze" for my rather humble "career", but it really helps. With a compressor you can have your cake (low EQ) and eat it too (smooth-out volume/tone levels). If (unlike me) you use a lot of special techniques to emphasize some notes, you'd need a good compressor (~$200+).