Try www.bcyfibers.com . They used to have an evaluation but I haven't been on it for a while. Personally I like BCY 450 Plus. I change mine (string and cable) every year and use the same bow for 3D and hunting and the string doesn't stretch using 450+. I plan on trying 452 as I believe it gives you a little more versitility in the number of strands you can use. Have used BCY DynaFlight 97 and it was okay as was S4 (but tended to be more "brittle").
Just to hit on a pet peeve of mine and not down any companies but I feel you should change the string at least every year and the cable(s) at least every other year. I feel that companies that charge an excesive amount influence the shooter to not change as often as they should do by either price or conclusions that since it cost so much it will last longer. No matter what material it is it will get the same amount of abuse from you. At one shop I helped at we'd get the majority of bows in with broken strings (under the nocking point) just before hunting season and be told they were about 4-5 years old.
On a side note, making your own string/cable isn't rocket science and for a small cost you can do your own. I made my own jig and think I have about $35.00 into it. There are various videos and sights to help you with making them.
Sorry to ramble.