help me build a cheap second system

I'd be very tempted to do something along the following lines:

Magnepan MMG at $600/pr
SVS Dual 12" sealed subwoofers at $1000/pr
Onkyo PRSC 5509 (recently discontinued, but still available new in box) pre-pro at +/- $2000

That's half your budget. Just add a reasonably powerful amp and source(s) of your choice with the other half.

IMO a pair of MMGs plus a pair of high quality subs integrated via Audyssey xt32 gets you a ridiculously high quality, full range speaker system for the $. If planars are an issue for you , you could also look at some other main speakers. I use Ohms (as well as MMGs) in a similar set-up to wonderful effect, but that's another $1k or so out of pocket. To date, I've not found anything nearly as impressive from the upper bass on up as the little Maggies at anything close to their price. Of course, everyone's MMV on that point.

BTW, the Onkyo is an excellent piece, too. The internal DACs are very good and it even includes a decent phono section. I replaced preamps from ARC and Joule with a 5509 several years ago and haven't looked back. There may be other xt32 empowered front-ends out there these days worth checking out in place of the Onkyo, but I haven't personally heard one so I won't comment.

Just one more way you might think about going.

Marty

Since your accustomed with great transparency and dynamics(TAD) the ATC SCM-19v2 is your speaker. At $4300(retail) it does take up a huge chunk of the $7k limit. There are many used options to keep this around $7K, here are a few. 1-NAD 375BEE/565BEE, 2-Yamaha A-S2000/CD-S2000, 3-Denon DRA-CX3/DCD-CX3. The Denon set up is the most cost effective, is 75w/ch enough to drive the ATC? It's claimed it can drive a B&W 802 Diamond! With the NAD you have the most power and a great budget player. The Yamaha S2000 series would probably push you over the $7k budget but your getting refinement and build quality over the NAD gear. The Denon CX3 series is also very well made but the mid-size components might be a turn off. With cables I would look at Signal Cable-Silver Resolution. At 35lbs the SCM-19 needs a quality stand which you could find used. FWIW a used SCM-19(NOT v2) model could be had for < half the current model. But from everything I have heard(read) the new tweeter and cabinet justify the cost. Since ATC does not update very often you should have a current model for at least another 5 years.

scrolling thru this thread, and not having a dog in this hunt, i'd vote for bob reynolds' recs--active speakers are the way i'd go (haven't heard the neumanns he recommends, but they look great on paper + would obviate the need for a sub). i know atc also makes powered monitors of high regard.

I can only offer for your pre amp look for an
Adcom 750 or The Gold. Read the stereophile
review. A Nelson Pass design with mosfets.Look
for one with the blue circuit board and it can
be run in passive mode.
Pair it with a pair of Monarchy Audio Pro MS 70
in balanced mono block mode.(80 a side.) Both
the Adcom and Monarchy amps are class a
designs.On ebay the amps are 700 for a pair and
The Gold if you can find one around 600 if your
patient.
Use a short run of reference 3 anti cables. Get
the speakers you want but splurge on XLR Darwin
The Truth cables. Your at roughly 3500 leaving
you 3500 for speakers Cd player and another
pair of Darwin Cables The Truth interconnects.
This system
fits the music you like.

If you can find a Dynaco SCA-35, pick it up and have it refurbished. It makes about 17 watts per channel and has MM phono preamp built in.

A cheap CD player that sounds quite decent is the Oppo.

If you can find a set of Realistic speakers with the Lineaum tweeters you are all set. If you want to go more upscale on the speakers pick up a set of Audiokinesis Jazz Modules; they are easy to drive and very satisfying.

The result is a revealing system with plenty of jump, easy to listen to and not a lot of money.