I would go the liberalism route and use it to nab nationalism. Build the taj, use the extra production to finish off building universities. I wouldn't push the war with Cyrus (and eventually Hatsheput) yet because your economy is still pretty young. Give your cities and cottages some time to grow. Get that research rate back up to a respectable 70%. If things go well you'll be launching charges with cavalry vs their longbows and will steamroll everyone for the win. Otherwise you're going to be locked into a slower war and it'll stagnate your economy. I mean your research isn't bad now, but it could be a lot better.