[inquisitor]

Unfortunately I'm not aware of any external 3G data device that would support more than three frequency bands. The Qualcomm Gobi 2000, an internal MiniPCIe card, is the only pure data device I know that supports quadband UMTS (850/900/1900/2100) and also GPS. There are a few quadband-UMTS phones (e.g. the iPhone4(s) and few Nokias) and the Nokia N8, which afaik is the world's only pentaband-UMTS phone, but these devices don't support antenna diversity (two or more antennas used to improve reception and thus bandwidth) for all frequencies, while afaik those Huawei hotspots have.
Anyway I think most of the UMTS850/1900-world (especially North America) doesn't have any attractive prepaid data tariffs, so support of these frequencies would be of rather little use.
Note that UMTS800 (only used in Japan) is actually not a separate UMTS frequency band but just a channel-wise cropped version of UMTS850 - every UMTS850 device does flawlessly work on UMTS800 networks so I do not count it as a separate band.
Btw I just realized that the E586 also supports the newer WiFi standard 802.11n (supporting up to 300 MBit/s), but I don't see any significant use in this as it's internet connection (21 MBit/s) is still way slower than the old 802.11g standard delivers (54 MBit/s) and further WiFi transmission power level is relatively low so WiFi range won't be improved significantly either and lastly I doubt people will exchange huge amounts of data within their mobile WiFi network. So this is rather irrelevant.