Sceptre is Trash, dont even try it, worst mistake I ever did was buy one, thank god for the return policy at the time.
Vizio as you already know has mediocre SD processing at best, so unless you intend to watch all HD stuff, it will get annoying, especially since better processing becomes even more necessary when you go from 37in 720p to 47in 1080p.
Toshiba has very very good processing, but the HL-167 is last years model, and there were some reports that certain models have greenish blacks. However it can be calibrated out if you goto the thread at AVSforum.com.
The Toshiba 40" RF-350 is by far the best in your list, and was a fall line refresh, it is a very nice TV IMO. Good processing, no green blacks, and a wide gamut backlight. If you are ok with going with the smallest of the bunch, for 999, that thing is a steal.
The problem with all the above models is they are 2007 models, and all the 2008's are coming out or already out and have better panels/processing from their previous generations.
Another thing you should do is go visit your local costco, and look at the Philips 1080p models they have, I cant think of the costco specific model # off hand but its 1080p and has rounded edges and clear plastic around the outside, compared to last years models which are square edged and have no clear border. This years Philips are a good mix of price/processing and features.
I currently have last years Philips, the 47PFL7422, which I got at Costco and I love the TV as it has good processing and a good picture. The blacks could be a bit better, but they certainly beat Vizio. If your costo happens to have the newer Toshibas (RV530, XV540 or XF550, grab one in a heartbeat)