1280x1024 is still 40% higher resolution than consoles render games at...
In HD terms, it is between HD (720p) and Full HD (1080p).
Your GPU is gonna struggle to play things at 1080p - why not just be happy with how your system is doing at 1280x1024?
To game well at 1080p, you're likely to need a new monitor, GPU and probably CPU... you have to decide if it's worth the cash to do that, but from what I gather you're fairly happy as is.
:EDIT: Well... Toms' GPU hierarchy chart puts your GT440 around the same class as an 8800 GTS 320. I had an 8800GTS 320 until this past month and was gaming just fine at 1080p as long as AA was turned off... handled Skyrim perfectly on high settings. The only thing it couldn't handle was the really GPU intensive games like Crysis/Crysis 2/BF3. However, pretty much anything made for a console - Mass Effect 2, Skyrim, Arkham Asylum, Borderlands - ran just fine at highest or close to highest settings minus AA.