For bathrooms, definitely go to a fabricator--the remnants are usually used for bath counter tops. The type, color and style will depend on what else is going on in your rooms. Post photos for better suggestions.

I agree and they all do not have to match either . Waht are you planning for the sinks ? More info from you will get more help from us. Post all info and pics here in comments DO NOT start another post.

Agree. Go to a stone fabricator and look for remnants. I built new and for my bathroom vanity, I found the perfect remnant for my 72" long counter.

You have to do the legwork to go to the different fabricators with fully measured diagrams in hand, with all the details noted, including sink center, plumbing center, finished edges, and overall length and width, accounting for overhangs. Let the remnants that you find, drive the design. You can’t be picky when using remnants.

Take cash to the fabricator please. The IRS is never going to know about the missing remnants.

I like the idea of a cash discount but unfortunately, if something goes wrong, it limits my recourse.

For the 30" vanity, could it be less expensive to purchase a new vanity and sink unit with a countertop already built in? (If your current vanities are good quality, forget that idea.)

Big box stores then to have some pretty yucky bathroom counters - cultured marble and the like. Have you looked at solid color Corian? Less expensive than a lot of other surface materials. Very stain resistant, though not heat resistant so you'd have to be careful will curling irons if used. Their faux stones and marbles are tacky but the solid whites and creams can be nice. I've used them in my kitchen and laudry room and think they are great.

You can also check to see if you have any stores that specialize in pre-fabricated counters, too. We have a couple in our area where you just go, look at the counters in the various sizes and configurations, and buy it on the spot. They were considerably cheaper than having remnants fabricated in our area (northern CA) because labor is so expensive here, but still provided more stone options than big box stores. (We did end up going the big box route in the end because of our less common vanity size and are happy with the quartz top we bought sight unseen, which through pure dumb luck matched the vanity, also purchased sight unseen, pretty nicely. That could easily have gone sideways, but we figured in a worst case scenario, we'd just return the top.) If you are in a less expensive part of the country, you may do just as well going through local fabricators. (We did do that for our shower curb and pony wall top because they were an unusual size, and were very happy with that experience--we got to go and pick out the particular remnant we wanted and they just charged us for the stone and the time to cut it.)

Prefab really only works for standard sized vanities, though, so for the 56" one you may find it challenging. It might be cheaper for that one to replace the entire thing with a 60" vanity if you have the space for that.