Muddy loins

Ah great, I hoped one of the cyclocross heads would turn up!

I've been looking at the Avid Ultimates, you'd say they're worth it? They'd work fine with the s500 levers?
If I was looking at a slightly cheaper option, 40-50 is there good options? or should I just go for the extra 20-30 quid?

Don't know if I'm just misreading, do you mean 20-30 per brake? cos i can only find avid ultimates at being 70 each, so 140 for a brakeset (extra £60+ to the others) feels alot!