I moved up when I hit $650, but that was just a personal preference. I'm glad I did, because I took a 3 BI downswing before making any money. If I only had 20 BI, I would have felt like I needed to drop back down (meaning I would have to win back 7.5 BI @ $10NL). I prefer the cushion.

As far as taking a shot goes, I wouldn't mix tables, but maybe only play one. It gets confusing as hell to play tables at different stakes.