I had made up my mind that all I needed was the ASN, but when I actually sat down and compared the requirements for a BSN and ASN side-by-side, and then looked at what course work I'd already done for my previous degree, I found that the only real difference time and money-wise between the BSN and ASN was two courses. Two courses! I thought that in the grand scheme of things, that was nothing
. So I went ahead and did it all at once (I knew that for me, personally, once I got out of school I wouldn't be going back anytime soon for those extra courses to get the BSN after the ASN--made much more sense to just go for the BSN). I have no regrets--the hospital I currently work for couldn't care less if a bedside RN has a BSN or not, but they're VERY picky about management having them. So in a few years when I'm ready to leave bedside nursing I'm already set.
Kind of a long reply to just say "Go for it!" If you've already got a bachelor's the BSN may not be such a long reach, and it's probably going to pay off in future for you. The key is, find out ahead of time what coursework from your previous degree will be accepted by your nursing program. If they get picky about some lower level undergrad stuff, like sociology or humanities, remember that you can CLEP a lot of the basic requirements.