M1330 to external monitor woes: endless problems with HDMI-HDMI and HDMI-DVI

Quite a frustrating afternoon. Any help would be very much appreciated.

I just got a Samsung SM2032MW, with a resolution of 1680 X 1050 and I'm trying to hook it up to my M1330 via the HDMI.

The 2032SW comes with a HDMI in, so I'd like it HDMI to HDMI, allowing me to use the monitor's speakers. But no go: whatever I do the desktop is, besides being far from crisp, off the screen by about an inch all round.
It seems that the problem is that it is recognized as a 1080p monitor: the monitor says it's receiving a 1080p signal and Nividia control panel recognizes it as a HDTV. But in display settings I do get a 1680 x 1050 option - choosing it, however, does nothing (and any other fiddling I've tried)
The monitor, incidentally, claims to 'support 1080p input' (presumably allowing it to take a 1080p signal from a Bluray or something and downscale it), so the problem might be that the monitor is fibbing to the computer, telling it it's got 1080 res. But even in this case I would still expect (a) it to downscale to fit or (b) choosing 1680 x 1050 from display settings to solve it (or can a 1680 x 1050 signal not be sent via HDMI-HDMI).

I have a HDMI-DVI connection more or less working with a workaround, but I'm going to battle on trying to get the HDMI-HDMI working. Any thoughts?

I have of course tried all the basics (installing/re-installing drivers, fiddling with nvidia control panel etc).

Thanks in advance for your words of wisdom!