The first thing I noticed about the average-sized MX300 PCI card was the gold-plated connectors in the rear, and the black anodized mounting bracket. While I seriously doubt that the audio quality is appreciably better due to the gold plating, it does look cool, and one advantage of the black bracket is the clearly labeled white text and icons next to each jack. If, like me, you've fumbled around behind your computer trying to read that annoying silver-on-silver embossed text, this is a nice touch.
On the mounting bracket, the MX300 includes standard mini-DIN connectors for the following: speaker 1, speaker 2, microphone input, line input, and the ubiquitous MIDI/Joystick connector. Like all of the previous Monster Sound boards except the M80, four speaker configurations are fully supported out of the box.
On the card itself, there are audio inputs for CD, AUX, and MODEM. Additionally, there is a wavetable header for a MIDI ROM daughterboard. Previous iterations of the Monster Sound series have had MIDI ROM daughterboards of various sizes installed out of the box, but the MX300 does not, instead opting to use system memory for MIDI samples. This is probably a wise choice, given the lack of MIDI support in almost all modern games and applications, and the fact that most computers have 32mb or more of memory.
There is also a proprietary MX-Link connector on the back edge of the card, to be used with an expansion board that Diamond hasn't technically announced yet. It's rumored that the MX-Link board will contain additional speaker outs, and digital input/output capability, to be more competitive with the Sound Blaster Live.