Thanks for all the suggestions everyone!! Some of them would be great, but I just don't want to increase the budget as high as some of them would require. I really don't want another car payment if possible, and at $15k we'll be pushing our limits of paying with cash.
The good news is, after looking into some more models, I think a midsize might fit the bill after all. My Grand Prix has 16 cf of trunk space, which is perfectly sized for fitting my gear.
Some of what I found (researching 2011s) are the Hyundai Sonata (16.4 cf trunk space) and the Mazda 6 (16.6 cf trunk space). 2011s right now are priced around $15-17k.
My only concern with the Sonata is it was totally redesigned in 2011...should I be concerned with that? I've always heard the best "time" to buy a car is the year after a redesign...after they work out the bugs.
This is a helpful list too...http://www.iseecars.com/cars/top-10-mid ... runk-space
I also like that the Sonata has a timing chain rather than a belt. Google didn't seem to want to give me a concise answer on the 6 (whether it has a belt or chain).