I am not certain how important multi-channel sound is to you. Myself, I would wait for a used sa-1 and not modify it. The stock marantz sa-1 and audio aero 24/192 are the best stock player's I have heard.
Modification sense depends on your budget, resale patterns, and existing system. I have only heard a/b of the higher end players, so I cannot comment on the effectiveness of mods to the lower players. I consistently read positive comments from people who have had the mods done.
I have the fully hotrodded (all the audiomod mods) scd-1, and it nukes almost everything out there. (Note: The audio aero is better if you like the tube sound). It does beat up on the SA-1, but the margin is smaller than any other unmodified solid state player, including the scd-1. The hotrod scd-1 has a cleaner sound, much wider soundstage, and superior bass slam & articulation to ANY cd playback I have heard.
My system's mods cost 3200. You can buy an scd-1 for 2300 so you are in the soup for 5500 for a ONE BOX world class cd/SACD player that has an estimated resale value of 3500-4000. My system's soundstage goes a good 10 feet past the room walls with the mods and perhaps 1-2 without. It truly does take my system to another level. If I take the player out I lose this effect. That's using a placette passive pre (1K), quattro-fil cabling(2K), an ayre v-1x(9K) & eidolon speakers(13K). This means the cd player is 5K/30K of the system cost. Good value to me.