Camera Bodies, puzzled

[amelo14]

I currently own a Canon XT and have been using it for a few years now. I have read that one should pay much less attention to the body itself ---obviously when the technologies remain similar to each other in different bodies, for instance XT, XTi, Xsi----- and one focuses on quality lenses. I have different high-quality lenses (Tamron 17-50 f2.8, Canon 85 f1.8, Canon 60 macro  f2.8, Canon 70-200 L f4 USM  ..... ; most bought given Bob's truly helpful and unbiased tips! ).

I am clearly conscious that equipment does not make a photographer, but I am truly puzzled and wonder whether I should just use my XT until it "dies a natural death", or should be thinking of going now for an Xsi (Or maybe even 40D) as the QUALITY of the images themselves would be really improved , with of course, all other aspects remaining the same (ie. same good processing, same good lenses,  etc.) 

For instance, I am currently thinking of purchasing the Sigma 30 1.4 because I am somehow deeply drawn to the normal perspective such as Henri Cartier Bresson used. If I keep the XT, I can go ahead and look at the sigma 30 1.4 and let the XT "dies it natural death". However, if it is best to change the XT, then the 30 1.4 must wait a bit longer (UNLESS Christmas is really good to me!)

[Bob Atkins]

The XT is a very decent camera. Even though it's "only" 8MP (vs. 12MP for the XSi), unless you're making large prints (over 11 x 14), I doubt you'd see a really significant difference in image quality.

If you wanted features of the XSi (like LiveView, better AF, dust resistant sensor etc.), then it would be a reasonable upgrade, but if you're happy with the XT features, I'd be inclined to stick with it for now if your budget is limited. The EOS 40D might be an even better bet then the XSi (again, depending on the features you want), though the cost is a little more.

Certainly if you want a different "perspective", such as that offered by a fast normal prime like the Sigma 30/1.4, then you might see more differences in your images by going for the lens rather than a new body.

[mjperini]

You have a nice selection of good quality lenses so you don't "need" the 30 1.4. The focal length is covered by your relatively fast zoom. That having been said I completely understand that sometimes we "see" differently or more clearly with a particular lens. I feel that way about my 35mm f/1.4 "L" even though I have the 24-70 f/2.8. My bias is toward the classic "wide field" perspective (I shoot both FF 1Ds3 and 40D) I tend to use the crop sensor camera for telephoto work which I do less of now. I'll often take just 2 lenses with the FF camera, the 35 1.4 & 85 f/1.2 and zoom with my feet. I think I get better, more thoughtfully composed pix. If you think you will, you probably will.
Keep buying the very best glass you can afford, and change bodies when you're no longer satisfied. When you do decide to change bodies I would follow Bob's advice and go with the 40D. It is a metal body, more rugged, more similar layout to the pro cameras. The 40D is capable of awesome quality. I had a 20D before that which my daughter has now ,It's still a wonderful camera.
One strategy I did employ is that I always bought FF lenses "just in case" and it payed off (for me anyway) when I got my FF camera. Now the prices of FF cameras are dropping very rapidly. The original 5D is a marvelous camera whose value is coming down quickly. Digital hardware does not age gracefully.
I love my 1Ds3, but the new 5d mk II has the same resolution with perhaps 2+ stops more sensitivity for less than HALF the price, ONE year after the 1ds3. I understand it and I am happy about it because cameras just keep getting better. But whatever my next camera is, I'll still have great lenses.
I hope this helps.