So far these are the only cabinets I can find that would fit, be an appropriate style / look we are going for: 48"wide (50 1/2" space on sides of fireplace), 30"H or 50" H (or 70" or 60" H as they are stackable). Our mantle is 60"H.

I could do the same height cabinets on both sides of the fireplace or I could do a cabinet on the left side and then do a cabinet or no cabinet on the right side (window side) with a chair/lamp.

Cabinets also come in black.

• 48 1/2” wide x 18 1/4” deep x 34” high.
• Interior space is 47" wide, 15" deep, 19" high.
• Mirrored 3-door accent cabinet from 55 Downing Street.
• Tan linen doors; black finish interior.
• Ring pull handles.
• Leg assembly required.

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Since your hearth is much deeper than the FP, it seems like a perfect opportunity to make them that depth. Here is an older post from here with the same issue - http://ths.gardenweb.com/discussions/2475195/built-in-bookcases-around-a-shallow-fireplace

There are many pictures online if you Google - see some here -
Fireplace with built-ins

Here is a picture of one that has a fireplace that is more shallow than the surrounding built-ins -

Thanks @my3dogs, I have been searching google, pinterest and houzz to get an idea on if it would look too much like a hole or not-- this is a good picture to illustrate what I was thinking. This doesn't look "bad" design wise to me. Thanks for the example! I'll check the other thread as well, I was reading through some last night but couldn't find my particular problem.

@RoseDruckman, that cabinet is great! I've never used lamps plus before-- I'm going to take a look through the website now.

I like the second image more as we have a dog and don't want to have smudge marks on the glass all the time. I think we would need lamps/artwork above the cabinets to give them some height as well.

Your bookshelves do not need to be that deep. 8-10" is plenty deep - prefer 8". Take the cases to the ceiling and put cabinets underneath - the bottom part with the cabinets will be deeper.

Rose that is a very pretty alternative to putting built-ins where built-in cabinets are really not meant to go!

Custom millwork always looks classy and expensive (so long as its done well). I would say mantle height or all the way to the ceiling. Don't build anything around a piece of equipment that isn't a permanent fixture. I would also recommend a mirrored tv instead of the big black abyss that tv's can create. Shelf depth is negligible, depends what you want to store there. If you go all the way to ceiling it could be deeper at the bottom and shallower at the top (above the mantle height). Good luck.