I have owned a few cabs, including a H&K Triamp Custom cab as well as a Bogner 4x12, and a few others.
Definitely the box has a huge impact on the sound quality, not just the speakers.
And hands down, best cab I have ever played through or owned is my 1973 Marshall straight cab with original greenbacks. This is followed very closely by my friend's 1971 slant Marshall with G12H bass speakers. That one is darker, but as well amazing sounding.
Get an old one with original speakers, they are something completely different, trust me.