There are still plenty of good emulsions available in 5x7. I wouldn't shy away from the format for that reason. Do bear in mind that an f5.6 lens for 5x7 will have very shallow DoF when focused at portrait range - you'll not be losing out on what you're used to with say an f1.4 or f2 lens on 35mm. Modern plasmats probably offer the best combination of price, availability and quality. There are other lenses out there that may be "better" in certain regards, but they're not going to hit that sweet spot of being affordable and highly functional (some may not be available in a shutter at all, or may have an ancient Betax or Compound shutter that will have very limited shutter speeds, most not fast enough to allow use of the wider apertures with today's films, and/or lack a PC connector for flash synchronization). I have a 240mm Heliar f4.5. Fantastic lens, beautiful portrait rendering, but it's in a Compound #5 shutter which has a top speed of 1/50th. Even if I down-rate FP4+ to EI 64, in daylight conditions I can't shoot it much more open than f11 (frankly there's nothing wrong with shooting at f11 for portraits - if anything, the f4.5 is almost too shallow). And while it has a PC connector, the flash sync is unreliable. It may not be able to be made reliable either - I had the shutter overhauled by SK Grimes, and the flash sync still works intermittently.