STR-450s vs non-Mesa Siemens

[SBG200]

What's up guys? Gearing up to take the NOS plunge. I want to get some of the Siemens EL34's for my Ace. Yeah Mesa has the STR-450's, but these can also be found a bit cheaper from other places. Is there any compelling reason to go through Mesa and pay the $25 markup or should they be essentially the same elsewhere? KCA Mike said I can get them from him w/in Mesa spec, and other places also have them cheaper than Mesa.

Thanks