Confused about what seat to get next, need to decide today.

[BlackSheepPDX]

Current setup: 

DD2, 20 pounds, 6 months, SafeSeat 1, need to give seat to nephew EDD 4/4/11

DD1, 40  pounds, 3yr2m, Marathon, manufactured late 2007

We drive a Honda Element, so have loads of room for RF. 

Trying to figure out if we should upgrade DD1 and put DD2 in the Marathon (RF of course) or keep DD1 in the MA and get a new convertible for DD2.  Want to keep DD1 harnessed as long as possible.

Thought we had decided on a Nautilus for DD1, but then sitting her in it in the store yesterday, her shoulders looked cramped already.  She is broad shouldered and has a longish torso (she's in MA top slots). We got pointed at a Symphony 65, which looked like it fit her much better, but I hear the top slots aren't really very high, so we may not be getting anything useful by putting her in the Symphony over the MA. 

Either tell me what you think about the Symphony, and which kid I should get it for, or tell me something completely else that will blow my mind and solve this problem I seem to be going in circles on.  Help please? 

ETA: Now considering the Frontier 85 for DD1...thoughts? 

[an_aurora]

The Symphony is ok but nothing spectacular.  I'd look at the Frontier or Recaro ProSPORT for her :)