If you don't like the feel or missing aftertouch but do like the Korg sounds, you can always buy a good controller keyboard and a sound module like the X5DR with it. One plus with the X5 is that it weighs very little, and is easy to carry around with you where ever you play. Controlling the sound is important too. The X5 offers a decend pitch-bend, a modulation wheel that stays in the position you want and can be assigned to any controller including aftertouch. Keyboard splitting allows you to play different sounds simultaneously, for example playing a bass line with your left hand is possible even while your right hand is playing a piano sound.
Some keyboardists only play lead lines.
For that you don't need any polyphony, and I'd suggest you take a look at a perfomance synth like the astonishing Korg Prophecy. Sequencing For sequencing the X5 is very popular for a number of reasons. It is 16 part multitimbral as most synths today. You can even listen to General MIDI songs with the X5 as it is GM-compatible, although the GM sounds are not that great. If you don't have a computer you might want to consider buying a synth with a sequencer built in.