You wll have to send your 800v3 to Meridian to get it to v4 - don't know what the cost is as I got my 800 new as a v4. what I can tell you is that the 800 v4 does have the capability to accept video inputs (composite, component, and s-video - although i have not done it myself, I assume it then outputs these though the HDMI output?) so you would not need to buy a used 562.

My Kit: 861v8+ID41, 800v4, UHD722, MD600, MS600, MS200, Oppo BDP-203, Genesis 201, Genesis 350 SE, Genesis S4-8 Sub, BG 520i, VTL MB450 II, Krell Showcase 7, Genesis 928 Subs, Danley DTS10 sub, SVS Ultra 16 subs.