Cyclocross - wider cross tires

I have been racing road for a year and endurance mountain bike races for a while now. In an attempt to stay in shape through the off-season, I ordered a single speed cross bike for commuting, trail riding and possibly some cross racing. I’d like to make it a little more off-road capable, so I’m thinking about getting some flared-out handlebars (like the WTB mountain drops) and some beefier tires (42cm max) to replace the 32 c Kenda Kwicks that come with the bike. I know with my mountain bike, there seems to be more advantage to having wider tires in the front than in the back, so I run a 2.25 in front and a 2.0 in back. I’m thinking about keeping the stock 32 c tire in back and getting a 38-42 for the front. There don’t seem to be a whole lot of options for larger cross tires. So far I’m looking at the WTB all terrain (38), and the Richey speedmax (40). I’m wondering if you more experienced cross guys might be able to tell me:

a. Should I just replace both tires, or would just replacing the front be enough?
b. Any suggestions for good tires in the 38-42 range and where I might find them?

b) http://cyclocrossworld.stores.yahoo.net/clinchers.html a broad assortment

could build race wheels with tubular rims , then another tire range is offered

http://cyclocrossworld.stores.yahoo.net/tubulars.html

I'm looking for a similar tyre to you. Unless you're willing and able to go quite a bit wider and into real 29er territory then I'd say to look at the high end adventure touring tyres. Eg the Marathon Extreme comes in 40mm. It should be a lot more off road capable than the WTB - just look at the tread pattern. There's some info on it in this thread:

www.bikeforums.net/archive/index.php/t-657731.html

b) http://cyclocrossworld.stores.yahoo.net/clinchers.html a broad assortment

..All of which seem to be 35 or narrower.