[LAU] using a condensator microphone live

Hi Sorry for the OT question, but I hope this list would provide me with valuable input. I'm using my sE usb2200A 48V microphone in my home studio, but now I'm considering using it live for lead vocals. Is that gonna be problematic, I'm (naturally) mostly worried about feedback? We're using headphones for monitor, but the house PA might cause problems. When recording vocals at home the singer is normally about 5 cm from the mic, was planing on the same approach live... Oh, and would getting a reflexion (http://www.sweetwater.com/store/detail/Reflexion/) make any difference? Any ideas and especially experiences with using microphones like this in a live setting are more than welcome. -- Atte http://atte.dk http://modlys.dk