Just my 2 pence worth,
The best quality route would be to simply get a DVD writer for your PC - that way your going digital to digital (so no/less loss) - with an AV DVD recorder for use with home cinema, you're likely to be connecting via scart - so you'll be going from the digital signal from the humax, to an analogue output, then re-encoded as digital. Also it will be a real time recording.
I have a panasonic DVD recorder (had it long before the humax) - and DVD-R's are in 4:3, for 16:9 it has to be a DVD-RAM (no idea why!!!), not sure if this is specific to the recorder I have / panasonics (its in the manual, not a user error). With the PC based solution, it will be in 16:9 or 4:3 depending on content.
Also, £25 for a DVD Drive for a PC plus around £40 for software, you'll make a saving aswell as a quality improvement.
I'm close to ditching the AV DVD Recorder in favour of a media PC, it might be SLIGHTLY more effort to start the software up, but if something is worth archiving, surelly its worth the extra effort?