Wow!! So happy to see someone finally built one.I've only just received the 300b version and am allowing for break-in and finding the right tube combination. But on first blush, it is very much the equal of the T2 but with more harmonic richness, density, flow, etc. all attributes of the 300b. Where the T2 is energetic, precise and emphasizes the leading edge of notes, the Megatron XL expands on the trailing end of notes, allowing them to bloom, hang and flow in space. Switching between the two is quite fun. I'll be able to comment further with more time.
We need to hear more impressions! How was the wait time?