Alternatives to Roland GR33

I currently augment my live guitar performances with a Roland GR33 synth module and a Yamaha G1D hex pickup but I find the Roland's sound set quite limiting and am considering moving to a software-based solution. For recording, I like EastWest's Play and Native Instruments' Kontakt Player, and I was wondering how a MacBook Air (smallest version) would handle these programs during live performance? I don't need a huge number of samples, as I only require some organ, strings, piano, trumpet and a couple of synth sounds. Would the Macbook Air have enough memory? (I'd rather not have to drag around a separate hard drive for samples but I guess if I could fit them on a memory stick...)

I would welcome any suggestions re. choosing hardware and software for this application.

As far as my guitar sound is concerned, I am very happy with my Fractal Audio Axe-FX II and intend to continue using this.

I have a great MidiFly for sale ... it's an awesome guitar in it's own right with electric and acoustic sounds bult in - then there's midi too!
http://www.soundonsound.com/sos/dec99/articles/parkermidifly.htm
Let's talk.
Dave

Why are you selling Dave?

Since the advent of harmonizers that respond to guitar inputs, I no longer have to rely on midi to get the signal to the vocal processor.. I don't use too many gimmicks when I play guitar, so the harmony was my priority - now that I have that ... I prefer playing my LINE 6 modeling guitar ... more guitar sounds and tunings. The MidiFly is an excellent axe - even without the midi, but I hardly ever use it. I suppose, it'd be fun in the studio to record doubling tracks with different midi voices, but I hardly ever record that way. I do a lot of "on the fly" (no pun intended) things, and I'd rather see this get used and loved than collect dust. I'm open to trades .. talk to me!
UD