is BAT good with non-BAT components?

I have a friend that have an entire BAT system:
BAT VK 60/ BAT VK 5i, CD-player and phono.

He had problems with VTL line2.5 in terms of bass details. He was advised that he had to get an entire line of BAT into his system what he now has.

Had anyone had any problems using BAT products with non-BAT?

What is good combination of BAT and non-BAT components?
I have a BAT CD player linked to a UNISON Mystery One pre-amp and a pair of UNISON Smart 845 SE power amps driving
Von Schweikert VR4's. They were not purchased at the same time but seem to work very well together. I did upgrade the tubes in the BAT (Upscale Audio) also the BAT is somewhat power cord sensitive. Fat Man and Fat Boy work best for me.
Good listening,
I have heard from my dealer who sells, both VTL and BAT that they are not perfect mates. However, BAT does match up good with other stuff. I've used Wadia CD players both w/ and w/o bat preamps, with a VK200 and vk60. Currently running a muse 9 sig cd/dvd into a bat vk50se/vk60.

just my take...
I am using BAT VK-50SE with Theta Dreadnaught with great results. No problem whatsoever.

There is nothing wrong with using all BATs. Everything they make is exceptional.
I am using a BAT VK5i SE with Aronov monoblock amps, a Muse 9 Signature digital front end, Linn LP12/Linto analog front end and Sonus Faber speakers. Works like a charm!
I just recently upgraded to a VK50SE preamp (Which blows away my old Sonic Frontiers Line 3) and it matches up beautifully with my Mark Levinson 332 amp and 360S/37 processor/transport. You shouldn't have a problem.
I use a BAT VK3i with Odyssey Stratus amp and have tried
several CD/DVD players and everything sounds great. BAT
makes great stuff! Someday, I'll have a complete BAT
The problem is the VTL preamp. It is not what they are known for. I would highly recommend the VK-50SE preamp for your friend, it is a wonderful piece that matches well with most equipment.
I use a Bryston BP-25 preamp into my VK-200, and the combination is very sweet and musical.
I have a Wadia 830 run direct into the mighty VK500....sounds awesome.
Larry K
I have BAT VK-D5SE CD, VK50SE preamp into Levinson 33H monos
into Aerial 10t's. Absolute synergy! I've seen many instances of BAT tube pre used with Levinson amps with great results.

I run a Wadia into the VK150se amps and it matches wonderfully.
I run a resolution audio cd 50 into the vk 60 and it works great. I'm currently selling the Bat only to purchase a powerful ss amp to drive inefficient speakers. Would be great to make monoblocks for current vk 60 owners.