Isen no7

HG800 cassettes are awesome. Ultegra quality to boot. Really need to be double the price, but we haven't clocked on to the fact they're as nice and charge pittance for them.
I mean, realistically, you could have always gone for SRAM's offering in 34-36, but I do prefer them Shimano qualities.

If I had to go carbon, I'd just hit up lightbicycle really. Order rims, order Bitex hubs in any goddamned configuration that you can dream of (50g heavier than a DT 240's). Spend rest on CX rays and a decent builder to lace them properly for you. Sorted.