High resolution models are not reccomended for multiplayer play, unless you have a powerhouse of a PC and beastly video card. OP+4 uses models of limited polygons for a reason.
However, there are boatloads of models available in the models forum:
http://www.dynaverse.net/forum/index.php/board,16.0.htmlI do vaguely seem to recall this "high res" model pack but not sure where it can be found and not sure that it isn't completely obsolete considering all the models posted since its release.
You might want to check out the docs on battleclinic.com as linked on our front pages, MrCue has accumulated more models than you can shake a stick at there.