I would definitely get a solo shelter, instead of a new two person shelter. You have a good two person shelter that you both like, so I wouldn't mess with it.
There are a bunch of great solo shelters out there, and a lot depends on personal preference. If I was a value shopper, I think I would get a TarpTent Contrail. It has been tweaked (refined) over the years, so I consider it to be a very good shelter at a great price. I personally like it because the apex is by your head. Other people feel the opposite, and prefer a mid type shelter (so you can sit up in the middle of the tent, instead of by the door). Mids also have the advantage of being a bit more storm worthy, especially since you don't have to aim them away from the wind.
Other tent makers I would suggest browsing:
Hyperlite Mountain Gear
I know I'm forgetting a bunch, but hopefully that will help (although it looks like you've already browsed some of these already).