Allison,
The 310R is great, but very expensive to operate. I have had landing gear problems with the one I used to fly.
The Grumman AA5 is a great plane, but though faster than your 172, otherwise not much better. They are more challenging (expensive) to repair in some cases, if damaged, than your average Cessna.
Have a look at Cessna 172, 177 or 182 RG. I particularly like the 182 RG, fast, easy on gas for it's speed, carries a great load, and get out of short strips well (watch going in though!). Make sure that the gear AD has had terminating action if you're looking to buy one. Piper Turbo Arrow 3 or 4 are also worth a look.
Avoid the Navion at this stage in your flying career, not that it's a bad plane, but it will consume more of your time and money than the others to do the same job, and will not be as predicable for operating costs.
If you just can't resist the older exotic types, go fly a Bellanca Viking before you settle. I put 30 hours on one last year, and remain in love with them, though they also have maintenance challenges, and can be difficult to pre purchase inspect well.
Have fun in the AA5...
Cheers, Pilot DAR