The real question is does the dvd player or your television do the better job of upconverting a 480p signal to a 720p/1080i/p signal.
Also note, if you're not already aware, that upconverting 480 to 1080 neither increases the quality of the picture not changes it to a true HD signal. It is a process of expanding 480 lines of information into 720 or 1080 lines.
Upconverting in the DVD player is a 100% digital process, so technically it is the purest way to do it which has the capability to be the highest quality way to do it, but to see the difference you'd have to be a real videophile.
Look on
www.avsforum.com for recommendations. The last time I looked, Samsung DVD players did a very good job at a very reasonable price.