Ok, well, what nationality are you playing? Uboat or fleet? Personally, I played the uboat for a very short while. I wanted to us OM from Lurker and check out this excellent mod. Other than that I stick with the fleets. There is a lot you can mix in match for the fleets. TMO, RFB and RSRD. I find TMO to very well rounded and simply fun to play, period. Just add historical traffic from RSRD but I think that would not work for you has RSRD creates historical traffic and in some areas can be slow for targets. Even so, RSRD is the absolute tops for historical traffic and major engagments. RFB is your harder realistic submarine mod. Combine this with RSRD and you have darn close to the real thing.
Truthfully, for you I would use TMO. I think it will fit what you are looking to fill.
http://www.subsim.com/radioroom/showthread.php?t=132330