Have to agree that if you struggle on a 5 mile commute --You need to get your fitness up. Won't take long but only ride every other day till it does.

The bike you have now is serving a purpose--Mainly you are riding it but the first bike only serves one purpose--To tell you what the 2nd bike will be.

You may like gripshifters right now- but they most definitely can be improved on. Style of bike and do you ride off road?- Is all or most of your riding on asphalt of hardpack smooth trails? Do you have any BIG Hills? Then is the current bike the right size? Once you have used your current bike to get fit--you can then start deciding what the next bike will be. Don't be in a rush to buy a new bike that may be wrong.

And I hate to say it but that is going to easy to sort out. The big problem for most of us initially is finding the right LBS (Local Bike Shop) They are not all the same but one of them will sort your new bike and sort you at the same time.