Call me compulsive, but I tend to favor the same "country of origin" for the board/stones/bowl combinations. Therefore, when I hear you mention Yunzi stones, I immediately think of my single-convex jade-tinted YMI stones, which look very "fitting" with my bamboo table goban, and my mahogany bowls (incised with Mother-of-Pearl still lifes)--together it cries out "Made in China"! If I were to "upgrade" to a rosewood floor goban from YMI that would be even more emphatically Chinese in appearance
That said, if you are considering Yunzi, then a question you need to answer is biconvex vs. single-convex, as this in turn dictates the goban (grid spacing on Chinese boards are usually larger than Japanese or Korean, and thus Yunzi stones tend to look "crowded" on non-Chinese gobans).
You also mentioned considering Korean agathis boards; I know on Ebay that a "6 Brothers" two-inch thick agathis goban straight from Korea goes for about US$190 ($130+$60 s/h) [http://www.ebay.com/itm/Baduk-Board-Agathis-Wood-5-5cm-Thickness-6-Brothers-/270482073522?pt=LH_DefaultDomain_0&hash=item3ef9fce7b2], but a similar (if not identical one) can be had from Yutopian for US$75+$13 s/h [https://www.yutopian.com/yutop/cat?product=TK110&category=T]. Samarkand (Janice Kim's defunct sales outlet) also carried these agathis boards, stating they were common in Korean baduk academies [http://web.archive.org/web/20040908230248/http://www.samarkand.net/Web_store/web_store.cgi?page=10D.html&cart_id=3206674_83612]. The Korean agathis boards tend to have a dark wood stain on the sides, and a "clear wash" on top to even the color of the wood, giving it a beige appearance--but this is not to everyone's tastes. That said, the contrast is pleasing to the eye, and would work especially well with colored JangStone Korean biconvex glass stones--the "Nano Silver" stones (which are not silver, but seaweed and candy apple green, respectively) are available from various sources, but are cheapest at YMI (US$39+ s/h) [http://www.ymimports.com/p-834-jade-color-glass-go-stones-nano-silver-jangstone-85mm-size-30.aspx]. The green color is reputed to be more soothing to the eye, and certainly would be very unique and distinctive in appearance. If you were more traditional, you could get black and white Korean glass stones of varying thicknesses; for example, Yutopian has a set of hefty 10mm Korean stones for US$36+$9 s/h[https://www.yutopian.com/yutop/cat?product=SK215&category=Sg]. As a finishing touch, the Korean mahogany bowls at Yutopian for US$45+$8 s/h [https://www.yutopian.com/yutop/cat?product=BK345&category=B] would match the brown sides of the goban quite well, though if you prefer the Go Seigen style bowls (wider, flatter) then the Lacquered bowls from Yutopian for US$40+$8 s/h might be the ticket [https://www.yutopian.com/yutop/cat?product=BK310&category=B].
Rounding out the "three country tour," YMI carries a Japanese KGT-made Kaya two inch table board for US$600+free s/h [http://www.ymimports.com/c-65-premium-japanese-go-sets.aspx], though YMI seems to no longer carry shell & slate stones separately. In the US Yutopian has a selection of shell & slate which vary greatly in price depending on quality and size (7.5mm "standard grade" is US$170 through 9.8mm "snow grade" at US$680) but you save compared to the various Japanese websites, esp. with regards to shipping [https://www.yutopian.com/yutop/cat?product=SK215&category=Sg].
HTH
DISCLAIMER--I have no connection or financial interest in any stores or web-sites (go or otherwise) other than as a satisfied customer.