Who said you're a bass? Your timbre is quite too lyrical for a bass, maybe even for a bariton. Frank Sinatra? That's a bariton. Hell, Geoff Tate I consider to be a bariton.
Then again, those vocal types is meant for the classical repertoire. Mariah Carey is definitely not a soprano, I would consider her to be an alto. Partly you can hear it from one timbre, partly it's how low one can go without using vocal fry. The same thing for someone like Pavarotti back in his 20s where he could sing a high f (above tenor c) in his modal range, that doesn't make him an alto, he's still a tenor.
It's like with a guitar and a baritone guitar. The total range of both are exactly the same, but they start in a different part and they end in a different part. Also a baritone guitar has more bass sound. So if you would play exactly the same melody on both guitars, you could distinguish them by the timbre. A baritone guitar can go lower without retuning the instrument, though. And technically(, if frets where infinite,) it could go as high as or even higher than a regular guitar.
There is a huge debate how you can distinguish the vocal types. Some say by timbre only (light and lyric versus dark and dramatic), others by starting range, others both (which I feel).
Then you could go to a doctor who could check your vocal folds and larynx in general. The smaller the construction, the higher vocal type you have, the bigger, the lower vocal type you have.
Then finally, there is the technique. People usually say, out of all vocal types, there are hardly tenors, which is not true (to me). The thing with tenors, is that the vocal range where they shine the best is near the passagio or passage or bridge of the voice, it's like you have to keep switching between gear 2 and 3 of a manual car. So some seem to not being able to go higher than a certain range, because of lack of technique, not because they are not tenors, same as a car which, because of a technicality, it can't go further than the second gear.
Your timbre is definitely darker than LaBrie, who is clearly a high lyric tenor, but I would never say you would be a bass.
Do you want to hear a bass? This is one:
https://www.youtube.com/watch?v=23cCpcUyrXYThis is a recent recording of me (yes, I need a lot of work as well)
https://www.box.net/shared/9kdoicn195