Emu and Proteus are pretty good but to be honest it is just a connection from a controller to send a command as opposed to an audio interface sending an audio signal so all makes are pretty standard and use the same protocol no diff in quality.

I would have a soundcard with midi interface built in to a custom build it has all the connections already in place and will be compatable as opposed to plug in an external interface.

Larry has made great suggestions but I am a PC guy and would plump for Cubase and a custom build DAW. Cubase can handle both audio and MIDI tracks in the same mix. Whilst Macs used to be far superior now the gap has closed and PCs are IMO just as good if not better. Each has pros and cons.