Difference between 1080i and 1080p unconversion?

[FF750]

I know this is primarily a Blu-ray forum but I'm sure I'm not the only one here with a big collection of DVDs that will not be replaced for a long time if ever. Because I love anime, foreign films, kaiju eiga, motorsports DVDs, and other non-mainstream stuff I have hundreds of DVDs in my collection that will be around for a very long time.

So that being said, having upgraded recently to a 52" Sony XBR4 I want my DVD player to do my TV justice but currently I have a Sony upconverter that's only 1080i. With the relatively cheap prices for good 1080p units now is the difference in PQ worth the 80-100 bucks for a new player? If you think it's worth it then would you recommend a particular model (I'm partial to Sony but will consider other good brands and don't really need a multi-disc unit if that helps).

In case you're wondering I have a PS3 for BD duties but would prefer to have a separate player just for DVDs.

Thanks for any input!