I will disclose that I am a Yama Seiki dealer. Yama Seiki is simply a US trade name and the name has only been around since 2000. The mills are built by AWEA and the lathes are built by Goodway.
Many know AWEA as the builder of some Toyoda VMC's but they have also been imported to the US under the Mighty Viper namea after which, Goodway bought AWEA. IMO, the AWEA is a very good solid machine at a good price.
Like AWEA, the Goodway lathe product by Yama Seiki is equally a solid product and like AWEA, Goodway is a master builder and one of the the largest cnc lathe builders in Taiwan. By master builder I mean that AWEA and Goodway build for many third party brands.
There are better machines out there of course ( and thee is much much worse); Yama Seiki is a very high value product, ie., you get a good quality machine (with alot of standard features) for the money your spending.
AWEA Web Site - CNC Machine Tools - The Ultimate Machining Power - Bridge Brings Performance
GOODWAY Web Site - CNC Machine Tools - The Ultimate Machining Power
YAMA SEIKI Web Site - CNC Machine Tools - The Ultimate Machining Power
you will notice all the sites run on the same theme
Hope this helps.