Round up, round up ... the gloves are off for the World Heavyweight MP3 player title ... drum roll ... and in the blue corner, Diamond’s “rock ‘ard” Rio 500 ... crowd cheers ... and in the red corner, Sony’s “nutter” NetMan ... crowd cheers ... ding, ding, round one.We first covered Sony’s NetMan a while back, but it seems that things have progressed somewhat to include a raft of new models from existing manufactures [Diamond in particular] and from some new kids on the block [MPman & Philips et al]. The Memory Stick Walkman will ship in Japan on 21 December for about US$430.Diamond’s Rio 500, is a USB connectable portable MP3 player that features a new visual interface with a larger, back-lit LCD display for viewing, a 64MB of built-in memory (expandable to 96MB) and up to 2 hours of continuous MP3 digital music. The player’s USB connection provides download speeds 5 times faster than parallel port connections. The Rio is compatible with both Mac OS and Windows 98 computers. Pricing of $270 USD, gets you a Rio player, earphones, a USB cable, carrying case, battery, RioPort Audio Manager software, and sample content [the Rocky soundtrack].These products are doing wonders for the MP3 market as it makes a once digital file restricted to your computer, mobile and free to roam in the real world. Sony pioneered this idea with their Walkman back in the day, but can they still pack enough punch to do it again?