I think the i5 will do fine. Check out my sig, thats exactly what I use. I do various projects, some are totally VSTi based with only a few audio tracks (running numerous streaming sample payers, multple Omnisphere sounds, Kore player stuff, lot's of plugs etc). Others are purely audio (I do location recording on a laptop then bring the tracks back to the studio, dump them to the deskside and edit/mix there.
I'm not familiar with the ASUS MOBO (asus has a good rep). I run a gigabyte UD4P and it's been absolutely fantastic. Reasonably priced, TI firewire chipset if you ever need to run Firewire, tons of ports, very good bios etc.
You might consider gong with a slightly heftier power supply. I have an Ultra 750 watt and it runs very quiet and cool.
Also, put a few bucks into good cooling fans. A DAW pc that sounds like a jet when you power it on is not very nice. My suggestion, Noctua makes some excellent fans that are darn near silent, move lot's of air at low rotational speeds.