Laptop options

I have just upgraded to SW 2009 SP3 on my old Sony Vaio whichhas ATI Mobility Radeon X700 graphics and although it works ok itis really slow. I have been considering updrading it for a whileand I think that this might be the time to do it and have a budgetof around £2500.00
I am not too computer savy so please excuse my ignorance with thispost.
I have my own small sheet metal/fabrication business and do all theadministration myself on one computer. This new computer would berequired to do all this by not only running SW but Sage accounts,Payroll and MS Office as the main applications (obviously not atthe same time). It would also need to be a laptop as I would use itboth in the office & at home (both with docking stations).
Due to this I would much rather use XP Pro 32 as I know everythingworks with this. Also, as I have only been using SW for less than ayear and as I'm still struggling to get to grips with it I don'thave any large files to worry about and out and out speed for SW isnot a critical issue.
I have looked around and from what I can see the Dell PrecisionM6400 seems to be the one to go for.
I spoke to Dell to ask what the difference was between the M6400and the M6400 Covet, I was told that there were some minor specdifferences (though he could not tell me what) but the maindifference was that the Covec had an Orange aluminium case. With aprice difference of £680.00 I decided there and then that Idid not like orange!

The spec I have looked at so far is as follows;

Precision M6400
Intel Core 2 Duo (2.4Gz, 1066Mhz, 3Mb)
Upgraded memory to 4096Mb
Upgraded HD to 500GB
Graphics NVIDIA Quadro FX3700M (upgraded to 1Gz)
Windows XP Pro 32 bit

Do you think this sounds OK, the graphics upgrade is over £400and I was wondering if it was worth it.

Any sugestions would be appreciated.

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