You are likely get the best performing amp from March Audio. His attention to detail is higher than most and his ability to service you should be better due to regional proximity. You can get more opinions if you like from others on ASR. As this is a DIY thread, you are off topic and so your query is getting less exposure.
As the (very knowledgeable)
@tomchr mentioned, there is no measurable difference in the buffers. But if you are an audiophile who needs to try them for yourself, you are better off with a Hypex NC500-based amp and then will have some spare cash to spend trying different buffers. In that case, would look towards the Euro suppliers. They generally have better quality than VTV. Hope this helps!