105 shifters and Ultegra mechs - consensus seems to be that new 10 speed 105 is as good as Dura Ace from a few years ago. Good enough for cross then.
Frogglegs brakes - utlitarian, effective enough to slow you down rather than stop you dead. Cross is about keeping momentum so you don't want brakes that are too good!
Mostly Planet X stems and seatposts, light Cinelli bars too. Compact chainsets - 46 and 48/36 with an Ultregra 25 cassette on both. Shimano pedals - long lasting and dont clog too easily.
Wheels and tubs - where I have spent my cash and treated myself:
2x aluminium - 1 set GP4 with 32mm FMB Orange SP and 1 set Race X Lite with specially made FMB Green SP with Dugast Rhino tread 34mm.
2x carbon with Dugast Rhino 32mm on front and 34mm on rear - better grip due to larger footprint.
I have a couple of old green Michelin muds on FMB and Dugast carcasses too for occasions as yet unspecified or for when I can find even more wheel sets!
Those wheel choices cover all the bases - mud, grass, rough track, fast and slow courses. Francois at FMB makes the most incredible tubs - top quality, true every time and with high performing tread and longevity. Dugast are great too but perhaps not as robust as FMB though the Rhino tread is hard to beat in North West conditions.
There are tons of items out there that are lighter, flashier and more bling-tastic. However, the stuff I use works time and time again, doesn't let me down in races, requires minimal maintenance and doesn't break the bank.