That might help for your SEO if you will restore them properly, add some relevant content to them, make a natural and relevant link to your website and it all will get indexed by Google bot. If you will make that accordingly to all those requirements – it’s absoultely white. And why not?

Those sites are worth of restoring only if – they still have pages in the Index and they have good-quality backlinks. In another case it’s just a waste of time an money. I’d recommend you to choose, buy, and start to work on the one … then analyse and continue working with others.