Celestion Alnico Gold 12",15 Ohm

Imagine a drawing made in paint, then one in Photoshop. That's the difference. At least on the clean channels.
i watched plenty of reviews online as well, but I can't even begin to say what a difference it makes in real life.
The biggest difference you will hear, is like i mentioned on the clean channel. Not even debatable - it's way better than anything, except maybe the Blue Alnico (that, i feel has 5% better sound, but less Watts - so up to your priority).
Distortion is a different story - you may like the Vintage 30 sound (an excellent sound of course) or you may like the Gold Alnico, which is a detailed sound. even the fuzz is more HD, which creates the sensation of a very "clear" distortion. if you use 90% driven/high gain sounds, stick to the Vintage 30s or the similar ones from the G series, but if your repertoire is predominantly on cleans, or maybe you just care for a more HD sound, by all means, go for the Gold Alnico - the biggest change in sound you'll get for the money - right up there with upgrading your tubes.

I have Bogner OS 212 and had installed V30s in it. The sound was OK, nothing special, with a "spike" that V30s are famous of. Then I swapped V30 for Scumback J75/BM75 combination, sound was improved over the V30ties, but still a little too boomy lowend was present and bought another pair J75/BM75 to install all of them to Bogner 412...Then I went to pursuit a perfect combination of the speakers for my 212 box....I noticed this beauties on the net, tried it in person on other amp and it was a love at the first sight/tone...I was looking for a speaker for pop/rock/country style of playing/music and after ordering it at Thomann and installing it in mentioned box, they really started to sing....And the most exciting part was, more the amp was loud, more musically rich sound was becoming. You just simply need to try it to believe your ears...If I would have to buy speakers for my 2x12 box, I would definately go with a Golds....