After opening the cab I can confirm that I have the cheaper version made out of particleboard. Now I'm a little bit unsure if I should just go on and swap em speakers or sell the thing and save up some money to get "the real deal". Quite frankly I don't need two 412s and my JCM 800 cab sounds amazing, I just want to have some Vintage 30s as an alternative to the G12-65 speakers in the JCM800 cab.
I guess it depends what sort of a tone you want.
Preamble: I heard some cool tones out of a homemade 1 x 12 made out of scr@ps of flooring. It is probably the coolest looking cab ever. Getting a 'good' tone doesn't always mean copying what sounds polished, high fi, and 'in style'. At the end of the day, it is all about what YOU like as well as how YOU wish to make music. The best tone is had by improving one's playing in terms of precision, clarity, as well as 'feel' and 'tone'.
That being said, what do you hope to gain?
A friend of mine who builds amps tells me that the sound is 70% speaker and 30% cab. I'm not entirely sure I fully agree with that. I'd say more 60% speaker and 40% cab, but that's just me. The long answer is that a speaker has a certain sonic footprint and certain frequencies are emphasized over others. A cabinet imparts a passive EQ onto the sound of the speaker by amplifying certain frequencies and attenuating others. This is really a mathematical thing based on the dimensions of the cab and the resonance frequencies of that cab.
In my experience with DIY cab building (I know a carpenter) and speaker selection, I'd say that certain speakers prefer certain cab designs.
For example: I have a Mesa Boogie 27" Royal Atlantic Extension Cabinet. It's a ported, wide body 1 x 12 and it has a Celestion mc90 (Mesa spec modified CL80). This is usually a somewhat fizzy and 80s sounding speaker. Very meaty sounding with a notch in the upper mids and an emphasis on the low mids. It tends to take the frequency footprint of a Dual Rectifier and accentuate it in an unpleasant way. In this particular cabinet, the speaker manages to sound quite British and it co-operates nicely with the Recto.
The homemade 2 x 12 is a copy of a Mills Acoustic Mach212B and it is quite an oversized unit. 32" by 20" by 18"
The cab also seems to accentuate the same frequencies that are predominant with the mc90. I had a v30 and an MC90 in that cab and it was dark and low mid heavy. Almost TOO american. It sounded good but it needed more high end.
I replaced the MC90 for a Warehouse Guitar Speaker (WGS) ET90 and the cab just came alive like crazy.
The result was a more British sort of a tone which was comparable to the RA 27" 1 x 12. So, the interaction of the speaker with the cab produced the tonal result.
Short answer: I think your best bet is to find the cab that works best with your guitar, pickups, and amp. Then you can decide IF any speaker upgrades will be necessary. This will save you money and headaches in the long run, trust me.
For metal, I'd recommend a Celestion v30 with a WGS ET90 in a 2 x 12 or 4 x 12. the upper mids of the v30 and the highs of the WGS ET90 give a nice, wide tonal spectrum. Another popular pairing is a v30 with a G12k 100.
Anyway, people have mixed opinions on speaker mixing but I'm of the opinion that you can mic up both and actually get more complex and interesting guitar tones. I know the X pattern is a favourite for blending but I'd be more incline to pair the speakers right and left for a more stereo 3D sort of a sound.