I'm a Hartke lover. I don't play all that much any more, but my big cab is still the old Guild/Hartke 410 with a Mesa Bass 400+. For what it's worth, I think the aluminum speaker cone thing is mostly hype. On the old Guild cabs, the speaker cones are definitely lighter than paper cones would be, but they're so flexy/floppy that any claim of stiffness is a joke. For what it's worth, I do think the Samson/Hartkes (current stuff) do have slightly stiffer cones.
I often hear people say that they think the sound is harsh, but I actually think it's the other direction - if anything, the Harkte is less trebly than most 4x10 cabinets. Less bassy too. I can't stand Goliaths - the horn is just too scratchy and annoying to me, but even with the horn turned off they seem brighter than my Hartke, not to mention being quite a bit larger and heavier. They do have much better bass as you get down to the low end.
The big downside of the early Hartkes was that they have very low power capacity - I can't remember it off the top of my head, but I'm pretty sure the sticker on the back says 240 watts max. It doesn't get really loud, but for low- to mid- volumes it's got a great tone.
David Fung