Yes, you will need 16 ohm speakers to replace them with if you want to keep an 8 ohm load...That would allow you to add an additional 8 ohm cabinet in tandem if you ever wanted to...If you went with 8 ohm speakers, you would have a 4 ohm load...No real option to add an addtional can in tandem, but you would actually have slightly more power if you used 8 ohm speakers....

My opinion runs a little contrary to most players these days....I am not fan of Celestion speakers as I came up on EV12Ls....I prefer to use high power speakers with less color to them...Especially in a combo amp with an open back....Vintage 30 really is the wrong speaker for that situation IMHO....I tend to think just about anything that is rated at 100 watts or more is going to work a bit better...That's just a general observation....

A newer speaker that I started using about a year ago is my current favorite...If I could use all EV12Ls, I would...But they are too expensive and way too heavy for me. I am using Jenson Jet Tornado. It's a Neodymium speaker that is rated at 100 watts...I really dig the tone and it weighs 4 lbs...Fairly coset effective as you can find them for around $140....

EVM-12L is my choice. The GT12x-100's are OK, but the EVM-12L is a cut above. I just haven't been impressed with the Eminence speakers I've tried. Yep, heavy and $$$, but worth it to me. And they are as tough as speakers get - I've had good luck buying used. Your EBay link above is from a seller with 100% positive feedback and he's giving you a 14-day return period, so the only thing you'd be out is return postage.

My favorite EVM-12L story: Quite a few years ago I was invited to sit in with a another band at a private house party - huge house (estate), huge party, and the band had their full setup (one of the guitar players had a Marshall half-stack and the lead guy had a Soldano full stack). I showed up with my Boogie 1x12 combo, loaded with the 12L. They set me up right next to the lead player and the smirks were flying looking at the little 1x12 next to the full stack. The smirks stopped after a couple songs. That was probably the loudest I've ever had the Boogie cranked, but damn if that single 12" didn't have all the presence of the full stack - absolutely no problem cutting through the mix, and the tone was very nicely defined. Truly the epitome of a 'giant killer'.

The SV MkI I've been using at the band studio for the past year or so had the Vintage 30 put back in, as I've had the EVM 12L I used to have in there in my MkII. Since I decided to start gigging with the MkI again I picked up another 12L (used on EBay BTW). Had it loaded in the amp for practice last week. The next day I was talking to our other guitar player and he was literally moaning about how good my tone was and how he needed to do something with his setup...

I might have to check out that Jensen wiht the Neodymium magnet Space. How close is it to the 12L?