Upscale audio advice

I have been looking to change the tubes on my BAT VK-30 from the Russian made 6922/6h23 which work fine but am looking into upgrading them. I looked at the Upscale selection and a few options initially caught my eye. These are as follows:
1)Amperex 7308 vintage gold pin
2)Amperex 6DJ8/ECC88 Bugle Boy
3)Ediswan CV2492/6922
4)Mullard 2493/6922 & Mullard E188CC/7308

All of which, if I choose their Platinum grade, range from $70 to $110.00 each which seemed pretty reasonable to me. The problem is, their sales guys tells me that none of these are suitable for my Pre-amp. He goes on to tell me that the only units that will work are the very same 6H23's that I already have. Is this sound advice from them given the fact that I would like to spend some decent coin to upgrade or do they not wish to deal with me? I have seen in other forums that they tend to want to sell to customers who have purchased equipment from them. Is this true? I do want to change my tubes given the fact that they are about 5 yrs old and definately are due for a change. I find it hard to believe that the only option they have that will work with my VK-30 would be these cheaper $35.00 per tube units. Any further comments anybody may want to add to this or advice you may have for me?