Bob,
there are several good amps on the market that can fit your needs. Roland KC series, either the 100 or 300 are both very good. They both feature 12" speakers. One has 60 watts and the other 100 and both have a mic input and multiple keyboard inputs. They are both portable and either to carry.
The Peavey KB/A 100 with a 15" speaker is also a very good amp but not quite as portable as the Roland models. However, a lot lighter then the 300 you used to have.
I like the sound of the Roland models a little better. The Peavey has a little too much "box" like sound to my ear, and the Roland is more natural.
For a portable speaker/amp I also like the Yamaha MS 60 powered monitor. It has one XLR connector and two 1/4 channels. It's very small and light weight and it sells for just under $500.00 If you want light weight, this is the lightest to carry around.
George Kaye.
One more note. For the last year I've been selling a portable sound system that's the size of a small 10" speaker cabinet made by a company called Prime. It features 2 mic channels with XLR connectors that can also accomadate 2 1/4 keyboard jacks, each with their own volume controls, a seperate CD or tape channel with RCA conectors, Reverb, Master Bass and Treble controlls and an external speaker jack connector which increases the 50 output to 100 with two cabinets. There is a speaker stand mounting hole on the bottom, the speaker is a 10" with a tweeter in the cabinet. It sounds really good, I sell more of these then anything else to my customers wanting good sound, a low price and lots of features. It sells for $250.00. It is made in Korea and it's not a major brand name, but it is great for small gigs.
George Kaye