ND Filter for a Digital Projection Lightning 15sx  

I'm looking to improve the blacks on my DP Lightning 15sx used in my HT. The Lightning specs 12,000 ANSI lumens. I know DP has a contrast upgrade for $2,000 or so which they say improves contrast by 30% or so from 450:1 to +- 600:1 at the cost off 5,000 or so lumens - leaving you with 7,000. (I can live with this). I'm told this is an optical retrofit which sounds like a ND filter add on. Has anyone looked into this. I'm using Minolta Lens'.