OK First you will not need a huge powerful PA but you will certainly need a PA with numerous inputs. You will also need an fx unit for your voice. This can be achieved by either a powered mixer with built in fx and matching speakers or a passive mixer plus a seperate power amp and speakers. You can alternatively have a passive mixer with built in fx and just connect it straight into powered speakers these are generally called active speakers. I use top of the range gear and play largish pro venues so my stuff power wise and price wise may be out of your league.
However if you want really good quality and do not mind splashing out a bit. Mackie systems have a wide range of powered speakers and do a really good quality mixing deck with a pretty good built in fx unit there are several models differing in size ie amount of imputs you may need. Add a microphone the one you have already that you recommend will do and you are there. One tip always go for a mixer and PA that is bigger than you need. You never know when you may need more imputs for extra mics instruments etc and that little bit of extra power for the larger venue.

Mackie SRM 450 a pair retails at around $1200 ($800 on ebay)more than ample power for your needs and very light to carry. well compared to conventional speakers.
Mackie passive mixer $200 and upwards seen several on ebay
Any questions just ask.

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