Preamp vs processor for upgrade

I currently have a computer based system that consists of a macbook running either direct or an airport into a musiland md-10 dac into a b&k st202 amp powering infinity kappa 7s. I am looking to add a preamp for better sound and more source options, potentially including a turntable in the future. Would i be better off spending $300 or less on a preamp and keeping my musiland or selling the musiland and getting a used processor for $500 or so. I listen mainly to music but will run movies through the system as well (in stereo) and might add a sub but am unlikely to go surround. I had a rotel rc990 in the past and was happy with it, but it seems some of the used processors might be a better option, most would require an external phono. any suggestions on equipment?
I don't know how good the musiland DAC is, but you can get a pretty decent used Denon AVR in you budget and most have a decent phono stage. I would suggest an AVR 4800 or above. Lots of amplifier power there too.