The bike you currently ride is unfamiliar to me, so I can't comment on it, and since I don't know where you are or what your commute is like, it's a bit difficult to pick a direction to point you towards. Have you tried riding your projected route of 20-25 miles a day on this bike? If so, and if you were comfortable doing it, then you probably don't need to rush out and buy another bike. If you haven't tried it, I would advise doing so; at least then you'll know if it's going to be an option and can tell your local bike shop what (if anything) you had issues with.

As far as what to wear and carry: it depends. I wear biking shorts and tops because of the padding and quick dry properties, then change at work. I use panniers and always have my flat kit (levers, tube, pump), a couple of tools, clothes, shoes, lock, ipad, coffee, lunch, water and a pouch for my iphone, keys, license and debit card. I have grocery panniers for shopping. FWIW, my commute can be as short as 5 miles each way, or 20+, if I take the scenic route. My grocery runs are generally shorter, but can be as long as 10 miles each way. I use my regular commuter which is a Frankenbike (hybrid with drop bars and a mish mash of other parts) or I use my single speed (70's road bike). Either one does the job.

I'd recommend asking your shop and then trying out what they suggest. If your shop rents bikes, try one in the style they recommend on your route so you can compare it to how your current bike felt.