The MX300 and the need for upgrades
Fast to market
Diamond's MX300 sound card was the first Aureal Vortex-2 based sound card to ship with included support for 4 speakers. Seemingly designed specifically to counter Creative's then-recent release of the Sound Blaster Live!, the MX300 and Vortex 2 had a revolutionary sound technology Creative couldn't match - "wavetracing." Basically, wavetracing works by mimicking the real physics of sound. In a 3D game, the actual in-game geometry (the walls, floors, ceilings, and objects which make up the world) is used to filter sound effects. Sounds heard through a wall are more muffled at high frequencies and lower in volume, and dynamic effects such as realtime Doppler shift and sound reflections are seamlessly and automatically integrated.
We're not going to rehash the whole story of the MX300, or go in depth with a comparison of the SBLive! and MX300. But what we can say is that Creative's got Diamond creamed in the "professional features" department. Creative's Emu 10K1 processor allows for a multitude of programmable realtime DSP effects and mixing capabilities, and more importantly, included support for many more forms of digital input and output than the MX300.
God is in the details
The MPC-3 compliant MX300 has 2 stereo outputs, a line in, and mic in. The SBLive comes with the same external connections, but also includes AUX, CD-IN, TAD (Telephone Answering Device), I2S, S/PDIF IN, and Digital CD-IN. The Sound Blaster Live Value, Creative's direct competitor to the MX300, is missing only the I2S connector. The MX300 only includes AUX, CD-IN, and TAD. Of course, the non-value SBLive! costs roughly twice as much as an MX300, and also includes a digital I/O breakout board which contains MIDI In/Out, Digital DIN, and coax S/PDIF In/Out.
In other words, the MX300 has absolutely no digital input or output on the board, as shipped. While this was no problem for your average gamer (even the "hardcore" who shelled out for an additional set of stereo speakers for 4-speaker surround), it took Diamond completely out of the running for the digital-enhanced crowd, looking to add such aspects as the "desktop theatre."
Room for more
This is what Diamond planned to address with the special 34-pin MX-Link connector, a header included on the MX300. The promise of future "MX-50" and "MX25" upgrades would allow for full digital input and output, as well as support for 6-speaker 5.1 surround output. Well, unfortunately, the MX-50 became a discontinued product before it was even released, but Diamond had to make good with the promise of an upgrade. Thus, after almost a year after the release of the original MX300, the MX25 upgrade was released. And here's what you get: