I had a Sharp XVZ-10000 back in 2002/3 I think and I had it until November 2012, when an upstairs hot water tank burst and flooded it.
Even of this vintage it offered Component, HDCP and 1080i and was a DLP projector. It was about the size of the alien mothership from Close Encounters, and had a fan borrowed from an Ex British Channel Ferry Hovercraft.
When the insurance came through I went and auditioned a few projectors and was gobsmacked at how little the picture had improved. I was really expecting a revelation - but although black levels were better, etc, I was expecting a night and day difference - and I didn't see one.
If I were you I would hang onto it until this 4k nonsense gets sorted out - another year or two and you may see a really good reason to upgrade.
Actually they weren't all DLP - I saw an Optoma and the Panasonic - but the room was not anything like a bat cave which won't have helped with reference to the black levels. The Optoma didn't look much better at all, but the thing which I noticed most of all with the Panasonic was the lack of image 'POP' that you get with DLP - the image felt dull and lifeless in comparison.
With projectors it is as much as case of where you auction as much as what you audition I fear.
I ended up buying an X35 (blind purchase as it happened). It was a toss up between that and the Sony HW50. In the end I went JVC from their track record and have been really pleased with it - but I'm sure I would have been just as happy with the Sony.
Mind you the XVZ10000 was a £ 10k PJ back in it's day - so it should have been good.
My point is however, that the 350 the OP has is a pretty neat machine - and I would be hanging on to it for a while longer until the newer 4k pj's get sensible price tags - from everything I hear that will be not too far away.....
That doesn't cost a bomb, bought this from richer when they had the last few for about £2k, I think the picture is awesome and I've had it for about 3/4 years and in the past that has meant huge strides, I'm under the impression that is less so this time around?
Quieter! I can't hear the thing and it is behind my head. Even on high power mode I'd hardly call it a racket, although it is audible.
I did sent it back not long after getting it due to an electrical fault, and they apparently cleaned or replaced the prism/optical block, maybe they changed some other stuff too.
I think I'll look at JVC and Sony in about a year, especially if it means I can get the user friendly goodies JVC seem to be dropping from their cheaper models.