Go the 40" - it's worth it.
I have the previous gen V series which was 720 and it still looks absolutely stunning.
The V series are the best value for money. They're not cheap and nasty, they're not over the top with shit you won't need - they're the balanced purchase and an amazing investment. Haven't had ANY issues with mine (touch wood) and Sony are one of the BEST brands when it comes to reliability on their televisions according to Consumer testing.
Also, Sony's look absolutely stunning as computer monitors (their resolutions are always mapped pixel for pixel it seems) so I say go for it.
Although, I'd try and drive that price down to $2050 incl gst.

*taps nose*