Use Dropbox or similar where they just host the file, whatever file you put there... Soundcloud (and I have one) is for fans, sharing etc. Mix feedback is best gained by using the highest resolution file you can that's a reasonable download.
I will say that there are a lot of newbies in the MP3 forum at the moment. It's not always this way. You have to remember that this is a place where people help each other. I post occasionally and listen occasionally, and mainly to people I know from being around here, or people whose posts seem interesting enough to warrant 4 minutes of my time and some of my broadband allowance...
When I post, people whose opinion I give a rats about will comment and so will a few others, and so the circle expands. And in turn I'll listen to them.
Participate is the best advice. You may not get much action initially, but if you hang around here and get to know some people and are the generally helpful friendly dude I'm sure you really are, then people will take an interest in your tunes... may take a while but worth it - this is the best place of its type bar none.