I have played Volkl cyclone and it is OK but not a top of the line poly in my view.
Here are some ideas on mid $ polys that are very good:
1. Signum Pro Tornado $14.69 - holds tension, twisted poly better than RPM
2. Signum Pro Hextreme (or Hextreme Pro): $11.90
3. Tecnifibre BlackCode: $13
4. Tecnifibre RuffCode: $12
I have tried a bunch and like Signum Pro and Tecnifibre the best - feel is excellent and these do a little better holding tension. Lux is excellent but stiffer and does not last as long.
Lots of people like the Tourna poly's and they are under $10 but I have not tried them.