lack of stateside service and support is a real concern, as ralph points out
some china based vendors help solve this by offering free shipping back to location x where they do the servicing, and that can help some
some others reach a scale of sales in the usa or europe that they do set up a least a local repair facility, of course the lowest cost new entrants rarely have this sorted out
that said, tube amps are
-- usually pretty big and heavy, so any need for service or repair gets to be a bit of pain, and if the process requires a trip to china, it won't be by rapid courier, so prospective buyers like the op are well advised to think through these tradeoffs
-- not terribly complicated and circuitry is straightforward, so a local tech who works on tube amps can probably do the work