SlowJoeCrow

I'll bite, going with a 39T may be slightly low geared depending on your terrain and power, but you can easily find 40 or 42T 130mm BCD rings if you need higher gearing. The big question for both derailleur and shifter selection is what size cassette you are planning to run. A Shimano 9 speed derailleur with a standard (short) cage will handle up to around an 11-28 cassette, after that you will probably need an MTB part or possibly a road triple derailleur. Shimano 10 speed road shifters will work with 9 speed MTB derailleurs.
Chain retention is also a major thing, the best solution I have heard of is to run guard rings on both sides instead of the more common outer guard /jump stop combo. If money is tight you can use a front derailleur by disconnecting the cable and locking it down with the limit screws. You might also consider bar end or lever mounted shifters, I don't recall seeing any down tube shifters on cross bikes recently.