Kawboy pretty much covered the issue of porting and polishing, and the whys and wherefores and what-nots of it. Polishing is not hard to do at all, but you do need to know where to polish and NOT to polish, as Kawboy mentioned. Porting is something else altogether, and it's an art form. It also requires a lot of specialized equipment, set up time, adapters and tons of extremely dirty, tedious labor. The gains, as Kawboy said, will not be significant enough to warrant the expense. unless the "artist" doing the job has experience on several 1300's, he won't really have a handle on what the best shape should be, so you will be getting a compromise. It might be better than stock, but certainly not worth the expense. And, he also won't know enough about the head's casting to be damn sure he doesn't make a area too thin!
I've done a lot of porting on Honda GL1000 heads for myself (long story!), but I ruined three heads learning just how non-uniform they can be! And, I would never even consider doing a 1300 head for somebody who only has one to work with and in the end will only be running it on the street. Porting is just too expensive, labor-wise, to reasonably consider for the street, unless you are rich, willing to cut up two or three more heads and a serious street racer.
A lesser known process (except to a porter) you can have done to improve your top end power is to "unshroud" the valve pockets. I won't go into that too deep here because it would take too many illustrations to explain, but it involves some careful removal of material right around the base of the valve seat to help direct the flow of mixture into the cylinder for a better "swirl-effect", which means better combustion, which means better efficiency of what fuel air you do get into the cylinder.
Some guys just have the talent for porting from years of experience, but the danger still exists that their lack of casting thickness knowledge can get them into trouble if they don't have several heads to work with.
Unless you are looking for all out top end performance, as Kawboy said, leave the casting rough near the valves to maintain the mixture in a vapor state rather than condensing on smooth walls just before entering the cylinder. If you intend to run high rpm's a lot, then polish the hell out of the whole intake area, run a wild overlap cam and put up with the low end roughness!
Your big-bore kit will give you the biggest gains per dollar (or pound, or yen, or lira, or euro, or whatever you have!). Nothing beats cubic inches, as we say here in the U.S.!!!
FWIW, if you want a really smooth running engine, you might have that shop cc the combustion chambers to be sure they all match perfectly. It's easy to do and not too expensive. Everything they can do to make sure that each cylinder is the same will help smooth out the power. Polishing the combustion chambers (during the cc'ing process) and the tops of the pistons will also help prevent carbon buildup.
