Personally I would buy online, seems much easier to me.

Difffering opinions wrt warranty though. I recently bought a Inspiron 6000. Over here you get a 1 yr CAR warranty as standard and to boost that to 3 years it was and extra 249 Euros or 20-25% of the purchase price. I spoke to a friend of mine who''s pretty high up in Dell Ireland. He advised me that the warranty was pretty much pure profit for them, and that 80% of problems occurred within the first 90 days, 98% within the first year. In other words not to waste my money. I took his advice.

I understand however if you want a higher degree of comfort given your more substantial capital outlay.