The current Sony Desktop Reader emulates a PRS-700. The only difference this makes in the emulator is the number of font sizes (zoom levels) which is 3 for the PRS-505 and 5 for the PRS-700. So what you see in the Desktop Reader is the same as you will see on the PRS-505. All you need to do is copy the PDFs over via USB (either in Desktop Reader or Calibre, or manually by treating the PRS-505 as a disk drive).
Note that some PDFs don't display (reflow) as well as your test PDFs do.
Sony is about to come out with two new readers, the PRS-300 and PRS-600. The former is like the PRS-505 except with a 5" screen (vs 6") and no memory expansion for ~$200. The latter is like the PRS-700, with a 6" touch screen. The PRS-700 is in general better than the PRS-505 for PDFs because it has a zoom mode as well as a reflow mode. The PRS-600 at ~$300 looks to be a very good choice for those who want to read PDFs on a small screen. We don't have full details of the PRS-600 (due this month), so there might be a "gotcha" we don't know about, but my recommendation would be to wait for the PRS-600 to see if it fits your needs. See
Wiki: PRS600 for what we know so far,