Hi Matthew,
It really depends on where you would like to be. I usually advise guests to the following boutique luxury hotels (some have been mentioned already):
(arrondisements are in parenthesis)
Hotel Montelambert (6)
Lancaster (8)
Hotel Bel Ami (6)
Plaza Paris Vendome (1)(just opened)
Hotel de la Tremoille (8)
Hotel Rafael (8)
I admit that some of these might exceed E250 but if you are looking for something nice, unfortunately, Paris has very little to offer for less. Hope you have a nice trip and some pack warm clothes.
CDG 1K