newbie seeks advice

My dad was a big time audiophile when I was in my twenties many years ago. He started all my friends on that route in the 70's @ 80's. I drifted away when I started a business and it started eating all my resources (both time and money). Now, 40yrs later, I have inherited his system and find myself close to retirement, far behind the curve and wanting to update his system for myself. I would like to keep his core speakers and find some components to bring out the best in them. He had a pair of Bozak B-4000's backed on the high end with a pair of ESS Heil Elites. The system sounded very good to me when I visited him, but he was always having trouble with his amp and pre amp (an ESS 500 and ESS pre amp). I have been looking at a lot of hi-end used amps (Mcintosh, Levinson, Bryston, etc) because I think the Bozaks are power hungry. I really don't want to spend 20,30, or 40,0000 dollars on new equipment for a new hobby until I see if it sticks in retirement. Does anyone care to give me the benefit of your expertise on the subject? I would be very greatful.

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If you have any decent stores locally start by getting to know them and hang out there a little; hopefully they’ll be a good source to learn from. Ideally your local shop will let you start dragging some gear home to hear for yourself what you think. That’s the great thing about the old brick and mortar shops that sadly are fewer and fewer today.

If possible buy used or look for demos. I’d personally look at a Parasound Halo A21 if you’re watching the budget over vintage amps. 1. The A21 is a newer amp that sonically will blow those old amps away and 2. No worries of old caps and etc. I don’t know your speakers but I bet the A21 will work just fine but maybe those more knowledgeable on the specs will chime in.

Also many manufacturers will entertain a phone call or an email on your system if their components will be a nice match or not... at least in my experience.

Good luck.
I can give limited advice but there may not be any benefit to it.

I am a novice as well. I also inherited a system. And I like it.

At its core is a Proceed HPA2 (Levinson) amp (250 wpc) which is basically like two monoblocks in one (100 pound) case and an Audio Research LS-16 tube pre-amp. These drive a set of notoriously inefficient speakers....very very well. The original owner was very savvy as these two seem to pair well and also pair well with the speakers (Aerial Acoustics).

You don’t see either of these for sale used very often but you do see similar models of each. I’m guessing you could get both in good condition for well under $8000 and probably under $4000.

That is the full extent of the advice I can offer.

Edit: There is an HPA2 on eBay for $1770 (although the picture shows a BPA3) and an AR LS-27 for $3400. Bingo!
I, too, learned of high end stereo early, and had to give it up while I started my business, so I can commiserate.
I hate to say it, but your equipment is pretty old, and technology has only gotten better. I second Adg's advice and go try to get some listening time on speakers. The Bozak's and ESS were good in their time, but I think you can do better with a more current speaker.
If you are willing to buy used, you can save a lot of coin, and still get a super sounding system. 
That's what I did.

You might want to start with a Class D amp, because they can output a lot of power for relatively small cash outlay, and are relatively small and don't generate much heat..  There isa lot of controversy here, as in every audio topic, about the quality of Class D amps vs more traditional (A,AB, B) amps, but the higher end companies that make them have good reputations.  If you decide that they drive the speakers but you don't like the basic sound, you can always upgrade.  I would look at Wyred For Sound or NeuForce.

  Another thought--try to get a AV Receiver used, for next to no cost.  For example, I just replaced a perfectly fine Onkyo AVR from 2009 that outputs 130 watts in two channel.  I needed a new AVR that would work with my new 4 K TV.  My Onkyo has no resale value but you could pick up a high powered one on Craigs List or something and play with it while you determione how much power the speakers really need in your room.  After you experiment, upgrade accordingly

When I see the move by many audiophiles back to vinyl, and the prices that high end vintage equipment is bringing on many venues, I wonder just how inferior older equipment and older technology really is. I recently passed on a good deal for a Mcintosh 2500 power amp that had specs. rivaling modern amps costing 5X as much. If the specs are just as the root of its inferiority only its age? 
Saw an article recently about how some vintage mid-fi receivers (Pioneer SX-1980 for instance) are far superior to current mid-fi receivers. The prices for them reflect that as well.
The Bozaks due to age might need cone surrounds repaired. If so, check out millersound in PA. The king of driver repair. Cheers,