Native Instruments DOES offer a free Kontakt Player, and I believe a free Reaktor Player, as well.  These give you a small subset of sounds that let you use them completely free, trying to entice you into actually purchasing the full-blown versions.  There are not too many included sounds, but they DO sound very nice, and FREE is always cool.
 
In addition, there are EMU and Proteus sound banks available for Dimension Pro and for Kontakt, for just about every Proteus synth and sound pack that EMU made, as well as for the EMU II sample library.  I have a bunch of these, and they sound really nice.
 
Bob Bone
 

I've downloaded Independent and Kontakt player, both are good. I purchased the EMU expansion pack (on sale to boot) and found most of the sounds I used before with VX. I like how D. Pro categorizes them - far better than VX did. 
Thanks for reminded me of the D. Pro expansion packs!

This might bring our buddy Larry out of retirement (miss that guy, rants and all) but if you can catch Sampletank 3 on sale that may be an option.  It's full price is currently $249 but it would not shock me if they do a holiday push down to your price range. It is multi-channel. The sounds range from so-so to some that are outstanding .  Comes with 33 gigs of sounds so you are bound to find more than your share of usable sounds.  Overall a fairly easy to use workstation with nice effects and nice live performance feature.  Having owned Proteus in the past, I think the transition from there to ST3 would be fairly easy.  I know some of the Proteus samples are somewhat unique and have that 90's lo-fi quality that works well in genres like Hip-hop and electronica, but those samples are available as sounbdpaks for DimPro fairly cheap these days.  No, it would not have the Proteus filters but Sonar has decent filter options that can get you that "crunch".

I had the opportunity to upgrade to SampleTank for $99 and I opted not too. I wasn't overly impressed by the sounds, but this personal preference. I do use Miroslav Philharmonik and I'm happy with that.
 
I'm at a point where I have too many sounds banks to work with (did I actually say I had "too much" of something ). In any case, I've grown to like D. Pro although it would be nice if it would be multi-channel, I mean, TTS-1 is.