When is it time to move up?

[Reel Deal]

Want to get everyone's thoughts on this subject... when do you know it's time to move up?

I made my first deposit this past May (only $200), ran that up to a little over $300 and cashed that out in early July when I decided I was going to take a break from on-line poker for a bit. Left $25 at Noble and when I decided my break was over (mid-August) I didn't make another deposit, I just decided I'd take the $25 and see what I could do with it. Well, less than two months later and I've run that $25 up to over $500. When I first played on-line I was playing the $25NL full tables and Party and Pokerroom and having decent success. But for the last month or so I've been playing 6-max $50NL at various sites while bonus chasing and have done well enough to run that $25 up to $500. I've also won at least 5 sit & go MTTs (ie, the 30 player & 45 player tourneys) at Stars, Party and UB.

I guess the issue I've got is that while I'm doing well at the $50NL cash tables, I really don't have the bankroll to move up to the $100NL cash tables (i.e., bringing 1/5 of my roll to the table). However, the other issue I have is that I'm not really playing for the money (I have a great job that pays well), I'm playing because I enjoy the game, enjoy the cerebral challenge of getting better at the game and am a competitive person.

So, given that it's not all about the money for me and that I want to get better and face better competition, what are people's thoughts here?