I wouldn't say that it is best for most Sierra games, but perhaps so for the pre VGA SCI games. By the time that General MIDI was supported, MT-32 support became almost an afterthought. There was a short transition between, when the support for the unit is not that great and before GM was widely used in the games. They did a reasonable MT-32 track for the VGA game
Conquests of the Longbow, but KQ5 (the first Sierra VGA game) had neither good MT-32 support nor a GM driver. Sierra did supply an after market GM driver for some of these games, but not all. The SHP installers provide these drivers for that games that Sierra did.
For the pre GM games where there was a genuine effort put into programming the MT-32 track, it did sound great. You can hear what some of these games sounded like by going to the pages on SHP for these games. There is a flash player under the thumbnail of the gamebox that plays a piece from that game. For the games that had reasonable support for the MT-32, I have a recording that I made from my own MT-32.
KQ4 is the first Sierra game to support it and one of the first games ever to do so.
QfG2 is a fairly impressive one, too.
Conquests of Camelot also has a nice one.
Munt, while promising, still leaves something to be desired.
The SHP Munt page was made a while back and Munt has progressed some since, you can at least get a sampling of the difference between the real thing and Munt. Besides not being very accurate, it also has a couple of issues. First is the need for the ROMs. The ROMs are Roland's IP and as such a C&D was slapped on the original MT-32 emulator project. The status is still in somewhat of legal limbo. The ROMs cannot be legally distributed, but can still be found. The second issues is that the Munt driver can be a challenge to install it and cannot be installed on 64-bit systems at all.
Setting up an MT-32 on a modern PC is not that hard, but you do need to keep a couple of things in mind. You need to have a MIDI out or a game port and MIDI adapter on your PC. Many sound cards today do not. If you do not, you can get a USB MIDI adapter. If you go this route and have 64-bit Windows, be sure that you get an adapter that has a 64-bit driver. Finally, if you have Vista or Win7, you will need to install something like
Putzlowitsch's Vista MIDI Mapper to select MPU-401 or its equivalent for the unit. Physical connections are fairly easy. You just hook up the MIDI out from the PC to the MIDI in on the MT-32. There are standard audio jacks on the back of the unit for the output. You can route this back into the audio input of your sound card or directly into some kind of amp or receiver to hear it.
Edit, I just looked at your eBay link. That comes with an ISA card and breakout box. These are good if you intend to setup a dinosaur, but are useless on a modern PC. For that, all you need is the the unit, itself with power adapter and a few cords, like I described above. BTW, DOSBox works great with an MT-32 with nothing extra needed.