You referred to a system that lets you use 2 wireless mics with a single receiver? I didn't know that was possible. Each mic needs to be on its' own channel and receiver. The "dual" factor has to do with the receiver and its antennae (i.e., "dual diversity"). Not the # of mics it will support.
Your statement that changing to a condenser element from a dynamic element will yield "studio sound" is certainly not the case. A good element (SM58) will deliver great results (the PG line is their "budget" quality series, certainly not up to the SM58). A condenser element may be more sensitive than a dynamic, but that doesn't mean it's better. Some of the very best studio mics on the market are dynamics. You also have to realize that the condenser-based wireless mics eat batteries much faster, they are not nearly as tough to handle rough treatment by amateurs that typically use karoake, and are more prone to feedback and handling noise (due to their higher sensitivity).
Look at "dual diversity" systems that offer the "real" SM58 mic head, that run UHF ( most of the systems today do). Shure and Sabine do that, and many models offer anti-feedback processing.

thanks for the feedback :)

well, i just virtually checked the system out today. It's a Shure LX-88 II dual non-diversity wireless system with 2 SM58 mics.

The system reproduces nice sound. The only thing that bothers me is that the signal often drops out. One more thing, there's no experienced soundguy to be there everyday to take control of the technical problems which leads to inappropriate settings on the mixer.

The funny thing is that the people at that cafe bar have no idea about audio sound at all. They want to have studio-like recorded mixes for such a live recording setting (with karaoke-level systems) and i don't know what else to say to those people :).

The owner of that bar told me he would wanna upgrade to a better dual wireless system with condenser mics or some kind of dynamic mics that can pick up good live signal.

if you have time, please help me choose a professional system.

Sennheiser or Shure or EV or AKG....you name it.

Once again, many thanks in advance.

Daniel

Things to consider. Your environment. If you have a metal structure, then you may/may not be able to find a budget unit (and that is what you are asking for, a budget unit to perform in adverse conditions, reliably). You need to go to Shure's website, find the Frequency Locator page. Type in your zip code. It will tell you what systems are recommended for your area. Then you should look for diversity systems in your price range. Don't go to the music store and buy a wireless, EVER. Make them order what you need. They do not buy frequencies intended for your market. They buy what they buy and get what they get.

Shure system's work. So either your situation is not condusive to wireless mics, or you are in deed trying to use two mics on one receiver, or it is not configured correctly. You don't just turn it on.