you already have RealBand. lots of us like it and lots of others swear by other DAWs.

as for midi sounds, you have to decide whether the sound fonts you have are good enough or maybe some advice from other users can point you in the direction of soundfonts or instrument patches they think will suit you. yes you can spend a fortune on pro level sampled instruments but do you really need them? i mainly use RealTracks now but for midi i have the Edirol Hypercanvas (aka the Cakewalk TTS1) and in a mix i find the sounds fine for what I need

try RB and within it you can audition just about anything in the way of new sound fonts or instrument samples although you may need to use jbridge for 64 bit plug ins

so without spending any cash try RB first