Very nice he will love that 120, thats almost a perfect tank. Are you doing live plants? I think once the rhom gets larger (maybe even now) that it wont care about the smaller dither fish. The best Ive had luck with are the giant danios, they are very fast and lasted a few months in my p tanks. The regular danios were too small and slow... but I would try some giant danios if I were you.
Yes I cant wait to get that 33 setup, thanks again. I found some glass tops for it I had laying around and got the background painted black already. Now I just have to get some time/money to build a stand for it.