Planning out a PS-Audio Stack, seeking advice balance of hardware vs dollars avalible

Would love to hear from folks that have compared these components or can explain the changes they heard when adding any of these components. 

I'm in the process of putting together my last 2 channel system. I know the answer is try stuff out in your own home, but not really an option. So I'm having to do it based on best informed decision. Then a call to an agreeable dealer I'll never meet and wait for delivery. Sadly I can't even hear the amps without a 5 hour plane flight

The good: 
Currently I upgraded speakers to Sonus Faber Elipsa SE and very happy. Very forgiving in the room, nice soundstage which is my #1 want in a system. Tone of instruments from cello to piano great.
Streaming almost 100% through PS-Audio DirectStream. This upgrade brought the life and love to the SE's.

Now the bad:
Arcam A32 FMJ, all connected single ended. single M+K powered subwoofer. I have my own personal oversize power transformer 30 feet from the house, assuming its pretty clean; but, winter storms are harsh and lots of bumping on and off. Running a UPS with battery which gives me time to turn things off when this starts happening. I don't have a dedicated room, so the living room is home.

Lots of room treatments aren't in the cards; but I'm pretty good on side 1st reflections and floor, 8 foot ceilings that I can't do much about. Bass is OK, the 140W at 4ohms drives the speakers ok, although it is working harder than it should and I feel I can hear it strain and could be much more. The 2.5 ohm speaker load in the higher bass wants more current than I can offer. At listening levels there is a slight but noticeable background noise which I would like to be much blacker. Really wanting an even wider and deeper soundstage and more life.

If I were king and had unlimited funds I would go
BHK Pre and a pair of 300's
Balanced cables (thinking the new Marrow's at the moment)
Pair of mid size Rel subs
P12 regenerator, dedicated 20A, and PS audio power cables all around. 

Even with a generous discount all this isn't in the cards.

Right now the BHK Pre is a given. I talked with PS-Audio and using the DAC output for volume control has drawbacks I hadn't consider. This was their #1 recommendation if I did nothing else. 20 Amp dedicated circuit just needs to happen.

Amps I'm torn on. Everything I've read and from what others have experienced says the 300's are much better than the 250. But how much better, will I hear it with my constraints, or am I better served by spending those $$$ on a regenerator instead? Talked with PS-Audio and their take is I'll get better sound from a Pre + 250 vs the 300's alone, but you'll love the 300s. Awesome, but the other advice is get the BHK pre in my system above all else. After I'm done comparing sound like diamonds in a jewelry store finding the absolute best, I'm wondering if I would really be just grinning and totally content with the 250 a year down the road. 

How much and how will a P12 benefit sound over the same money spent on the 300's instead? PS-Audio feels that in the worse case with my power bumps it will power off and protect everything downstream. No clear opinion on sound improvement.

What sort of improvement might I see by going with new sub or subs over staying with the M+K

Min thoughts are BHK Pre, balanced cables, and a yet to be found used higher current amp. Thinking the right tubes could tune a better then I have amp. More likely to go with the 250 and balanced cables regardless of the amp choice. 

Adding one of the following would be in budget, ideas which is gonna add the most value? Upgrade to the 300's, better subs, or Power Regenerator? I can defer the last 2 but going to the 300's just kills them as options.

Love to hear from people that have heard these options and about their choices