I've honestly never been able to gauge just how powerful those ships are in comparison to Star Trek. If I was to make an educated guess, I'd say they get to at least 5.
The biggest feat of a Ha'tak came early in the show, when Stargate Command tried to destroy one with two naquadah-enhanced nuclear missiles. It was said that they had explosive yields of 1 gigaton, and they didn't even make the ship rock when they landed a direct hit. And their weapons are capable of overcoming other Ha'tak shields, so we can judge their firepower from that.
Apophis's flagship was able to destroy a Ha'tak with only a few hits, though Heru'ur was taken by surprise so his shields may not have been at full power.
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“Where the longleaf pines are whispering
to him who loved them so.
Where the faint murmurs now dwindling
echo o’er tide and shore."
-A Grave Epitaph in Santa Rosa County, Florida; I wish I could remember the man's name.
Their speeds are comparable. Ha'taks and ST ships anyway, 42,000 times the speed of light is max speed for a Ha'tak, and I believe that that's about Warp 8 or 9. Asgard ships make that look like nothing though.
Yeah, based on personal opinion and gut feeling I want to think that Ha'taks would be superior to 23rd century ships and about comparable to the ships we see in TNG and DS9, though I see the more powerful ones mopping the floor with Ha'taks.
I'm going to say that the Ha'tak stops at 3 or 5--even it's probably more powerful than the Enterprise A it's not as maneuverable and the ST ships have better combat range.
__________________
“Where the longleaf pines are whispering
to him who loved them so.
Where the faint murmurs now dwindling
echo o’er tide and shore."
-A Grave Epitaph in Santa Rosa County, Florida; I wish I could remember the man's name.