I would probably go with some suspension work like mentioned above by tomustang.
I did the TB/Plenum combo and to be totally honest if I hadnt gotten them used and for a really good price I would have been disappointed. If you can find a combo used than I would say go for it, but I would wait.
UDP's I have the piggyback style and they were a good bang for the buck, and I have had zero problems with them.
3:73's I would say they are a good investment and are perfect for a daily driver. I drive about 80 miles a day round trip to and from work and they are great. At 70mph I spool up about 2400 rpm. 80 mph is right around 3000 rpm. I have no regrets on them.
XCAL 2 not necessary until you do some more modding. I would wait until you have done all the boltons, or gears first...