Budget wise I still use K motion springs. I found the K1000H double gives me good life. Probably better out there but I doubt for the money. Do 11/32 on the valve stems...titanium retainers...keep the thing light. It adds big time to spring life.
PS: The roller springs that came on a set of Canfields I bought lasted 1/2 a season for the customer. Replaced with K motion and he now has 2 seasons on them. Just tested and they are ok. He turns 7300 in a flat.
When something works it is damn hard to get me to change.