I agree. V.92 modems will give you a bit better upload speeds If your isp supports them.
I would recomment only a hardware modem. IE onboard controller and onboard DSP. Stay away from winmodems since they make your cpu do all the signal processing work when it should be doing other things.
If you get an external serial modem, it will always be a true hardware modem, and it will not be able to overload your serial port, so max throughput is not effected.
If you go internal, I'd recommend an isa modem since it has way more bandwidth than a modem needs and you still should get one that is true hardware, to keep your cpu free for game performance.
Personally I use an off brand serial external modem, and get great connection speeds, 48000 lowest ever, usually 52000 or so. I've used creative modem blaster (POS), ibm internal pci modem, and some others and never got any better performance than I have now.