XP on Studio 15(55), Studio 17, Studio XPS 16

Greetings all. I have an Inspiron 1520 with an 8600M GT, running XP 32-bit. Unfortunately, the 8600M GT is on the way out. Fortunately, I still have a warranty. In the event that I am offered a replacement, I've a few questions about these models (which I consider the most likely replacements - correct?).

1) Can they run XP? I would likely run XP Pro 32-bit if possible. I'd seek to get the cheapest OS option I could on a replacement - Linux if it's cheapest, Vista Basic if possible otherwise.

2) What are my CPU prospects? I have a T7500 (2.2 GHz, 4 MB L2, 800 MHz FSB). The Studios offer a T6600 (2.2 GHz, 2 MB L2, 800 MHz) and P7450 (2.13 GHz, 3 MB L2, 1066 MHz FSB); the Studio XPS offers only the T6600, and the next step up is the P8700 (2.53 GHz, 3 MB L2, 1066 MHz). The T6600 is clearly inferior to the T7500, and the P7450 probably isn't quite as good (going by performance, not battery life). Would the P8700 be a reasonable expectation for a replacement? If a P8600 were offered I'd be happy with that, but it's not an option right now.

3) How's build quality? Other than the 8600M GT (which I can't blame Dell for), I'm quite satisfied with my bricklike Inspiron 1520, and am not certain the Studios or even Studio XPS are the same quality.

4) How insistent are they on taking the usual minimums on all categories? That is, I don't have any need for a decent HDD, WiFi card, or even RAM if it's a DDR2 notebook, and would be willing to take rock-bottom in these categories (even none at all, for that matter - I have aftermarket ones for my 1520 that I could just use again in a replacement) if it meant getting a better CPU, or the better battery (I have an 85 WHr with my 1520 and would like similar in a replacement). Is it negotiable to take subpar in one category to ensure equal-or-better than the original in others?

5) Any chance of a Precision M4400 replacement? Spec-wise, it's just what I want - decent CPU + GPU that would make a good replacement (nVIDIA instead of ATI, unfortunately, but probably post-Bumpgate), and rock-bottom in categories I don't care about (HDD, RAM, etc.). And the build quality is there. But as it's not a consumer line, I suspect the chance of it is near nil, despite the cost not actually being any higher than the Studio XPS 16.

6) What are the chances they'll try to replace it with a new Inspiron 15? The fastest GPU option on that is clearly inferior to the 1520's 8600M GT (when it's working, that is), so I do not want a current Inspiron. The Studios (1555 and 17) both have at least equal-caliber CPU's, so those are acceptable, but the new Inspirons are a definite step down in performance (and I suspect build quality, too).

Thanks in advance.