Hey there. Hopefully I can help...I'm one of the folk behind Cyclocross Magazine (http://cxmagazine.com)
If you're counting $1500 not including the frame, you've really got a lot to play with. Here are a few tips, hopefully of some help:
Spend the money on two wheelsets - a basic clincher set ($150?) and see if you can find a nice used set of hand-made tubular wheels ($150?). It doesn't have to be the latest and greatest by Mavic, and in fact, something built up from a pair of hubs/rims/spokes by a good builder will do great, and often be LIGHTER than the fancy $800 wheels with deep dish rims, etc. Tubular tires will cost you another $200 (vittoria's are around $70 each which are fine), clinchers probably $80, so we're up to $600 with glue and tubes...
The rest - choose your favorite drivetrain stuff. Doesn't have to be the highest level stuff, esp. in cross as the elements and crashes can really take their toll and cause you to need to replace parts more frequently than road. 105/Ultegra/Rival/Veloce stuff is great. We love campy ergo 10 shifters mated to Shimano drivetrain and a 9-speed cassette (you read that right) with a slight change in the cable clamp at the rear derailleur. The campy stuff just holds up well. (our issue 1 happened to have an artilce on just this setup). You can easily get the whole drivetrain for $300 or less, and might even have some parts lying around you can re-use, like a shimano rear derailleur.
Then, I'd go with strong, light aluminum cockpit stuff, like ritchey, bbb, or even kalloy guizzo stuff. You don't need carbon here! We've seen to many broken carbon posts and bars. $150?
For forks - a nice light steel fork could match the gunnar well, or a carbon one. By my math you should have $3-400 left for that and a headset and brakes. I think you could do everything with some creative searching and a little ebay for under $1k though.