First of forget the Paasche etcher. That size of "toy" is intended for jewelry or other very small jobs requireing intracate control. I'd go so far as to say that the area of coverage will be more about the size of a felt pen dab than a dime. It's intended for very small size and intracate jobs. Doing a bicycle is just not in the cards for such a unit. Neither is the normal sands or other media. In short that unit for a bicycle frame would be like trying to paint a battleship with a 1/2 inch artists brush.
The Gilmore gun at least looks more like what you need. But without knowing the actual consumption in volume at what PSI you're in the dark. In googling for "low volume media blasting" I turned up this interesting link;
http://www.harborfreight.com/gravity...gun-93221.html
Note the low volume of only 1.7 cfm. The compressor you listed shows a rating of 4 cfm so it should be able to keep up fairly well. This particular gun would appear to be fairly well suited to doing a small job such as a bicycle frame. And if you watch the video they do mention that this particular gun is only used with glass bead media. But from the looks of it doing a number on the painted metal it seems like about the right size and type of media.
You're going to need to learn a lot about media blasting. On any sort of good frame "sand" is the last thing you want to use. Most of the media grits which cut fast will also cut at the metal below the paint. The less abrasive media that will cut the paint away but leave the metal below intact are going to be a bit more specialized and likely not that cheap. Or if you insist on doing the job with the cheaper but more abrasive sand then you'll need to vary the operating pressure to set up a spray that minimizes any cutting of the metal. And when you do that it's not all that fast a job. Or as noted to use the glass bead media mentioned already.