I love my two Dells (Dimension 4550 and 4600). Even though getting the second one was a real nightmare as their staff couldn't seem to take our credit card pament properly!
One of the main reasons I like mine is that inside the case they are so tidy and they even include additional runners and clips for additional hard drives et al. When I installed some more memory in my Nan's HP machine it was horrid, cables just loose and catching on the motherboard
I also like the excelent diag feature, if there's a problem with the machine the leds on the back change colour and give you an idea what it is.
Why don't you tell Dell that you're being chased by another company and they can offer you the same cheaper, maybe they will do you an offer? I know they did with me when I had all that trouble with them