Yeah, very much depends how much you want to spend- stock towers are weak if you crash or flip, same with bulks,- the stock 3905 diffs are alright, but eventually even they will fail with a MMM setup or similar. Only if you're on a tight budget would I suggest sticking with mainly stock items. Like I said, its all very much personal preference for alot of parts- take a look around at other builds and see what you like the look of-, there are some nice variations around the forum on the 3905 platform, take this one for example:
http://www.rc-monster.com/forum/showthread.php?t=22113