My suggestion would be to look for a one or two international trips in L or U. An L/U gets you 3x miles (1x base, 1x bonus, 1x GM), an M or higher will get you 2x base, but the fare will likely be more than twice as much, offsetting the extra base miles. This assumes you don't mind travelling in coach.
I would have recommended the int'l weekly webfares (unfortunately none for next weekend), however as a web-only fare you won't be able to use a voucher for it's purchase.
You could do a Sat-Sun Mar 16/17 trip to Anchorage for $539, dropping to $470 if you ruturn Monday vs Sunday (K fare on the return). Flight miles is about 3700m if thru SLC, 3900m if CVG then SEA. There is also a routing through DFW, I'm not sure the mileage on that.
You might be able to do a European trip for the same money, close to same mileage, but I doubt you'll be able to do it with as quick a turnaround..
Those ATL-ANC flights were in L class, if you went before Mar 15, and paid a portion of the ticket (maybe token amount of $50), you might be able to qualify for an addition 5000 bonus miles. You'd need to look up the thread in the Delta forum for additional info on it. However, the price appears to be higher for that weekend ($578-$637).

Jeff