McCormack Amp Upgrades

Looking for comments on McCormack amp upgrades, either done by McCormack or other modifiers. I'm getting a DNA-1 shortly (stock) and am looking for a cost effective upgrade. SMc offers silver, gold, and platinum upgrades. Would appreciate any comments regarding upgrades they got and the difference in sound. Spending as much (or more) on upgrades as the amp cost is significant, and when you look at the total investment you could move up to a more expensive/newer amp. Hope to hear a noticeable difference when spending $900 or more on upgrades. You can reach a point of diminishing returns when spending this much or more on upgrades, as you sit in your chair and try to convince yourself that you are hearing something better. What have you tried or heard? Do you think it is worth spending $900 to $2000+ in upgrades for this amp? Or should I use for a while, then move up to a stock DNA-225 or something else like a Pass Labs X150 or X250? Speakers are VS-4.5. Thanks for your comments and opinions.