I know a lot about these amps. It's an awesome route to take because you will never have to buy another amp again... Just send it to Steve for whatever next level upgrade you can afford or he crafts.
That being said, you should actually just buy a stock DNA right now and send it to Steve for the most recent updates. Almost all the legacy updates like the Gold are pretty old and still have the original circuit board. Thus, they are near the end of their useful life and will have to be replaced anyway.
You can still buy the gold now and see how long it lasts you with the original circuit board. Who knows, it could last another 5 years if you're lucky, but I'm mentioning it so you won't be surprised if it doesn't.
All his current mods start with replacing that driver board which effectively resets the useful life on the amp, so that's your best bang for the dollar, highest performance, and most reliable option.