Is this still a pretty good unit to buy? And if so what the most you would pay?

If you have no side imaging, it's a good unit. The fish don't know it's a few years old. You'll be able to find structure and fish. Using it as is will be OK. If you want to upload the latest version of software available for it, do that before you start adding waypoints. Just easier that way. Might call HB to see if the software update is still available.
I'd offer $250 for it and see where that goes. You can get a new Helix 7 SI/GPS for about $650 or maybe less. Price on that will probably be going down since several new models are coming out this year.

There are two 898c SI units.

The 898c SI Combo is the first of the 800 series and has CCFL backlighting.
The 898c HD SI Combo replaced it and has LED backlighting-- easier to see in bright sunlight.

The 898c HD SI Combo was replaced by the 899ci HD SI Combo and that was replaced by the Helix 9 SI GPS and is the current model along with the newer Helix 9 CHIRP MEGA SI GPS G2N.

Sooooo, at the right price <$500, it would be a good unit since any SI is better than no SI.

Thanks! I got it for 400. Not bad I guess,