A quick size comparison: Mamiya C33, M262, Rollei 6008 Pro and 80 Planar, Nikon F6.
And compared to the TLR in profile. From the front the Rollei looks deceptively small.
The F6, while fairly bulky for Nikon's non-built-in-grip cameras, is almost as tall, but a downright featherweight in comparison.
Someone mentioned the SL66. Got to play with one not long ago at the inimitable Shot On Film Store a few months ago. Absolutely beautifully designed and crafted, all-out mechanical camera, and I entertained picking one up as well with my insurance money. Unfortunately like many cameras of Teutonic origin, they are fairly rare and seem to be more collectible—their production run went into the 90s but was fairly low volume. Finding additional lenses was nearly impossible when I searched.
Yet another that I recall: the later Hasselblad 200 series focal-plane shutter bodies. Again, pricey. Seeing a few in the $3-4k range on eBay right now. Inexplicably some including a metered finder—they already have in-body metering.
A couple people have also suggested Fuji's huge MF RF lineup, and perhaps some of those might interest you. However, the early interchangable-lens models don't have metering, I believe, and vice-versa; and the only 6x6 I can recall is the recently discontinued GF670/Bessa III folder.
Theres a couple other options out there—the Kowa Six and Mamiya Press series come to mind, but again, no metering. The later focal-plane Bronicas (EC-TL) offered TTL metering, but again, difficult to find and a reputation of conking out electronically.
I certainly appreciate Godfrey's closing quote. The film resurgence has bumped up interest in all cameras, but modern MF cameras were of lesser variety and lower production than 35s, of course.
Still think your best bet may be the Bronica SQ series with the later Ai prism. Affordable 6x6 SLR with electronic shutter speeds, shutter speed priority with a few prisms, and AEL plus spot metering with the Ai prism; stellar lenses and idiot-proof film magazines; motor-drive grip and TTL flash on the SQ-Ai body. Wouldn't hesitate to buy one again in a heartbeat. The only deficiency I ever came across was not having long speeds beyond 8 seconds, but its rare I needed them.
