What could be the differences between the Spendor A4 and A7 in terms of sound quality?

I’ve been researching the A4, A7 and D7 for quite a while. Generally forum comments lean toward the A7 (more base, fuller sound), the only trade off being the price difference. D7 is considered a step up, though many still prefer the A7 upper mids and highs. I’ve heard all 3 and am leaning to the A7. Cost isn't a consideration, i just don't want to make the wrong choice. 

What amp are you considering? The only thing holding me back is whether 35 PL tube watts will do. It seems that the impedance curve is fairly benign (min 5.7 ohm) and  should work, I didn’t detect and problems during a listening session. 

@kren0006 Thank you so much for great info! Learning a lot about speakers here in A'gon.

@glow_worm I am considering a used integrated Amp from PrimaLuna or a used Ma252 from Mcintosh for having tube pre-amp system. But, I am a newbie and will probably have to research on amp matching separately. I am totally unfamiliar with 35 PL tube.

Sorry...PL = primaluna :)

I’d think PrimaLuna would sound nice with A series, but haven’t heard it to verify.

FWIW, I use Audio Research DSI200 integrated amp with my D7’s.

I think both the A and D series are not too difficult to drive; pretty easy impedance curves as noted; not extremely high sensitivity ratings but decent.

As you probably know, A series doesn’t come with grills, so the drivers are exposed. I find that the A4 looks kind of strange because the mid-bass driver has a somewhat truncated look (don’t have full circle of material surrounding the driver - like sides are shaved off), almost like the cabinet is not quite wide enough, but that’s just a personal aesthetic appearance thing -- probably some people think that looks cool.

@glow_worm Thanks for clarifying that out lol There seems quite a number of used PL tubes out there and I would love try them out once I make the decision on speakers.

@kren0006 Yes, I noticed the A4s have the woofer edges cut out to have the cabinet shape. I thought it was okay, but seemed a little compromised sound-wise, externally. I’ve just read your posts about the A2, A4, A7, and D7 in other threads btw! Great help.