The Eigen is a touchscreen device and has a 528MHz processor, 128MB of RAM, WQVGA screen, GPS and even an FM receiver. Both the HQ and Eigen may have more than what I've listed, those are just the known features.
Not much is known about the Acer devices, just that there are four of them. I suspect it is some mix of touch and non-touchscreen devices and perhaps GSM and CDMA support.
The requirements to upgrade to Windows Mobile 6.5 are a device that currently has 6.1 on it, 128MB of RAM and a 400MHz processor. Just because you have such a device though doesn't mean it will get an upgrade. It is up to the manufacturer and carrier to actually provide the update.
LG and Acer are obviously targeting WinMo 6.5 with their devices but aren't willing to wait until later this year to ship. We know 6.5 is done but it will take a few months from that final compile until devices start to show up. Manufacturers have to add drivers for their hardware, like card readers, video, audio, etc. Then the carriers have to possibly write and definitely test the cellular radios to make sure they play nice on their networks. Finally, they then have to put their adverti...er...logos on the device so you'll never forget which carrier you are using.
If you are getting a Windows Mobile phone soon and want to have 6.5 on it later this year, be sure to confirm with the carrier they will be providing an upgrade. Don't take someone's word for it. Look for a press release or other written evidence that they intend to ship an upgrade later this year.