Expand on what you mean by clunkiness?
It's been a couple years (2011), but when I was riding a force equipped bike, I rented an Apex equipped bike while on vacation, and found that for the most part, Apex felt alot like Force in terms of shifting, though the front felt slightly less immediate (since Force had zero loss on front shifters). I think Rival and Apex should be quite similar in terms of construction/functionality, so I don't think that you're gaining much by going to rival, except a few grams of weight savings.
SRAM isn't known for buttery shifts, but when it's tuned right (and that takes a little more effort than I preferred, specifically the FD), it works as well as any of the other group sets.
I will also say that while I dislike BB30 bottom brackets and have heard of plenty of BB30's failing on Cannondales and Felts, I have zero confidence in SRAM GXP BB's at all. My outboard bearing GXP team BB failed in something like 600 miles--so having a pressfit GXP BB on the Giant sounds like a nightmare to me. Though, in fairness to SRAM/Truativ, they did redesign the GXP Team Outboard BB to be a little bit more robust and protected from grit in 2012, iirc. So perhaps they've learned their lesson and have applied those same design philosophy to their press fit BB's.