Im a fairly new 9velo owner and these are my first set of carbon hoops. Build quality is pretty spectacular. Run true and are far less obnoxiously sounding than the hubs that HUNT use when free wheeling.
Cheapest set in the range cost me £530 with shipping. They come with 4 years warranty but the problem with these is if you need a replacement freehub/body. You're going to be waiting a fair amount of time for it to arrive from China unless you try plugging a DT Swiss one in. Apparently a DT Swiss patent expired and now all these Chinese companies are rolling out copies of the hubs with their wheels but YMMV.
If 9velo is your choice and you pick the cheaper shipping option which includes pre-paid import charges. Expect to wait around a month for them to arrive.
Only been out for a small handful of rides with my RV55 set and so far i've been fairly happy with them. Hambini did a review of one of their more expensive disc wheelsets and 9velo gave him a discount code to use which I used to get a further 10% off on top of the current website discount. (I think i got 30-35% off in total??) Dont know if the code still works but ideally its up to you. Hambini rates 9velo quite highly so far and so has other reviewers - namely peak torque.
Peak Torque:
I chose the RV55s. Going with the more expensive RVL wheelset would have gotten me what I assume to be a better rear hub and CX-Xray spokes but i didnt think the increased price was worth it for me as im just a recreational cyclist that likes to go fast and occasionally peacock when doing laps around regents park (while being dropped by people on bikes worth 8-10x more than mine...)
If youre willing to watch some reviews.... there is another chinese brand called 'Superteam' that sells carbon wheelsets on amazon who have also been very highly praised on youtube - They are CHEAP but most reviewers claim to be surprised at how well they have held up. Being as cheap as they are, They might be on the heavier side.
::EDIT::
I bought the 55mm's because I live in london - (More potholes than hills...) but 9velo do have a 40mm set