How much can I get for a site with arounf half a million page impressions (almost all quality traffic)?

I have just applied to a bunch of CPM networks and got approved by one today and waiting for others. I want to go with the best possble one, so will wait a little longer before applying code for one of them?

Its an auto site, so how much can I expect to make? I know the cpm varies for differnt types of sites, but my site is a quality site with auto as its niche. 20-30 cents CPM is just not worthwhile for me when I can better utilise that ad space.

Also, how many banners must I display. I was hoping to display a single wide banner, you know the one that measures around 700 pixels wide and around 90px vertical just above the content?

Sorry, so far I haven't tried any CPM networks, but I have adsense and direct advertisers (who pay really well).