you will love a darn good office system.
I just set up my office, best sound I ever had here. first, I rebuilt/re-positioned my desk to allow a perfect equilateral triangle with my mains which are non-ported bookshelf speakers. I picked and bought used B&W D100i. (6-1/2" woofer size).
My desk is pulled back away from bookshelves on front wall, creating the triangle, leaving an aisle to access the shelves, but importantly allows locating my self-powered sub, old velodyne 12" re-coned, on the floor between the shelves and desk, tucked back, aimed sideways, simply adding low bass, not directional. I just add a bit of bottom with the sub, unaware unless you turn it off. wires from computer to sub, to adjacent bookshelves.
get the tweeters seated ear height as always.
separating low bass to the sub first, sending the rest to the amp/bookshelf mains is good, the amp and mains do not need to try and produce low bass.
four advantages:
1. bookshelf mains do not try to make low bass.
2. not trying to make low bass is how you successfully avoid bookshelf speaker designs relying on ports to try and make low bass
3. amp can be lower power, smaller, more affordable, more location options.
4. sub’s amp can be powerful to control woofer without costing a great deal.
I love tubes for my main music system, but you may want to rethink tubes, because the computer is on a great deal of the time, even when out of the office (the kitchen!), and when working, not listening, making heat, burning watts all the time.
I would not add a center channel to the mix, just get yourself the best centered listening position.
Prior to this, I was off-center and relied on the balance control to center things, ok, but centered for real is wonderful.
Video images perfectly centered to the sound is terrific.
