My message should have read "WoLAN" not "WLAN". Anyway, I have used Powerlines in the past to avoid hardwiring, but found a regular wifi connection to be more reliable. Powerlines do allow you to use the LAN card. But the connection depends on a number of factors, key is the quality of your eletrical circuits. One issue I had with them is that they needed to be reset (i.e. unplugged) once in-a-while and for me access to re-set was fiddly.
I've also tried the 'pocket router' method (apple airport in my case) which is also OK, and again allows me to use the LAN card rather than wifi dongle. However, using wifi seems to be generally a little less reliable than a LAN cable and I have not heard (yet) of a reliable WoWLAN, all of which is pushing me towards hardwiring the LAN. Next to the HTPC, I have a Swisscom TV box (IP TV) which, although running OK most of the time via WLAN (using the apple airport), sometimes struggles with a connection, whereas a LAN cable draped across the living room always works OK.
I got that it was WoWLAN and you'd have mixed issued with powerline [works well for me on single ring, not so good on secondary - hence the Wifi element - so all the unit is doing as acting as local WiFi <-> LAN bridge, so your never really using powerline for comms In effect, a replicant by slightly different means to your pocket router method
Reset and access, separate issue and that could be the killer
Cheers - JCMP