Upgrade advice

I am currently using a Mac Mini to a MHDT Paradisea dac via toslink cable to play my itunes downloads and cd's i burned to harddrive.

It sounds pretty good, but i want to take it to the next level. I don't have a lot to spend but was thinking of getting a Hiface adaptor and upgrading to Pure Music software. Am i on the right track? Are these worth $300? Thanks for your opinions.
I've been down this road, and have tried all kinds of options, both inexpensive and expensive....

The best I've ever heard a Mac Mini is toslink optical into a Naim nDAC. The optical cable is a VanDenHul and the Mac Mini has as much RAM as can be added and an SSD drive.

Amarra or Pure Music was used, but I preferred iTunes without them. I only use 16/44 Apple Lossless files, so I'm totally aware that others have different experiences, especially when using 24/96.

The Mac can sound extremely good when done simple and clean. I have owned several very high end digital units (Linn DS, Naim, 47 Labs, Meridian, etc...) and the Mac can not only compete, but consistently sound better in a lot of aspects.

Like I said, I understand this is not everyone's opinion, and I hope I don't get too many things thrown at me, but I can honestly say that a Mac done right, can be a revelation. Keeping it simple and clean is best....and don't forget to have fun.... ;)
If you are just sending PCM from a computer from lossless or uncompressed files, it shouldn't matter what computer or software you use. There's nothing complicated or non-deterministic about reading a file, decompressing if needed, and sending it to an output device. The only thing you have to do is configure the software so it does not modify the original "bits" of the encoded song.

The biggest bang for the buck in "upgrading" sound is speakers and room setup/treatments.
I thought i read somewhere that people were getting better sound using this hiface device in the chain. Said 16/44 sounded better with it in the chain. I am far from a digital expert but thought it would be a cheap ($150} upgrade.
Streetdaddy - See the comments in my thread regarding the M2Tech under this same discussion forum. You will see that those that have responded feel that it was well worth the money. I could not agree more! It made a very noticeable difference in my system. Also, I have to agree with Hellofidelity's comments. Using iTunes and keeping it simple produces a great sound IMO.