interconnect suggests under 300 used.

I would suggest replacing one cable first. That is the balanced cable from your primary source into the preamp. This where you should put your present $$$. Then, when your exchequer recovers, I would upgrade the other cables. If you do it this way it is a lot more fun. Cables from CD to Pre that I would suggest are Cardas Balanced Neutral/Golden Reference (try genesis168), Transparent Balanced Super or up, whatever Sergeui at Stealth suggests, Innersound Balanced (!), FMS, AlphaCore Sapphire or TQ1 if you can find one, and Acoustic Zen. When you want speaker cable in the future, check out Magnan as well as the other brands I mentioned. Have fun, but have more fun with incremental purchases!

I have tried many different cables over the years. I have come to the decision that Synergistic Research Cables are the BEST Sounding, It'll Bring the Best out in your system for the Money! Now that SR has ACTIVE SHIELDING it takes their Cables to a New Level ( World Class ). I'll compare them to Cables at least 2x the Price! All I use in My system now is SR ACTIVE Shielding Interconnects,Speaker Cables,and Power Couplers. Go to : synergisticresearch.com
You can Probably pick up a Good Pair here on AUDIOGON. Good Luck and Enjoy!

Good suggestions Ivanj. I usually like to work the other way around. A delicate sounding IC for between the CD and preamp - I find it better preserves the low level signal - followed by a more robust cable between the preamp and amp.

In my cable auditions I found that the second cable (between preamp and amp) was more difficult to finalize because the robust cables tend to have a richer sonic signature.

What three cables? Considering you have ML gear, I would work toward something like Nordost Quattro Fil between CD and Preamp and Cardas Golden Reference between Pre and Amp. That might sound nice. However on your budget... you might look at something like Audioquest Lapis or Nordost Red Dawn followed by Cardas Neutral or something from Tara Labs.

Lots of used cables on the market in this price range. I also own ES speakers and have found that a well designed pure silver cable sounds best (speed and resolution of low level detail). Brands I have tried are AZ, Silver Audio, and Pure Note. The Pure Note Sigma at $400/1m (new) may be a good match for your system.

I will increase the anti if the improved sound is worth the expense. I will up my budget to 600 for interconnects on the used market. Will this help?