Need some kind of HTPC/Media Server for both Win7 & MAC OS X

[nemesis379]

Need some kind of HTPC/Media Server for both Win7 & MAC OS X

What I need:

• A way of accessing files from either a HTPC I build or a NAS.
  
• Fast speeds 90-100MB/sec for transferring files and watching HD content off the unit.
  
• The unit to have decent speeds when connected to a MAC (which I'm looking at buying in the future sometime, I also have Windows PC's too).
  
• The unit to be able to watch netflix videos unless it's a NAS then I will use something like LG BP620 to watch netflix/stream videos
  
• Maybe be used as a FTP/Web Server at some point as well as the above.
  
• It has to be either 2 or 4 bay, and I will be wanting to backup each hard drive to another so 2 backup 2 use (not using Raid 1 or 10 because I don't think it's a viable solution).

What I've been looking at:

• Making my own Windows 7 HTPC but will speeds from Win7 to MAC OS X be fast enough? (Cheaper option compared to the rest)
  
• Buying a synology NAS, however I had the DS412+ a while back and it had problems with transferring large amounts of data it would go on standby.
  I wanted this feature but couldn't and had to disable so I returned the unit.
  
• Another NAS from another company. (I would have to buy something like LG BP620 to watch the content from the TV)
  
• Buying Mac Mini Server then adding external drives.
  
• Cheaper is better if it can do all that I need.

Basically I need centralized data whereby PC's and MAC's can access files fast without a hiccup, if the machine is running as an HTPC then it's a plus. If not I can get a LG BP620 and stream from the machine that has the data, but the machine must be able to handle HD content etc.

I already have hard drives (WD 3TB Reds x4), but I'm only using two at the moment 1 backup 1 use, so If I have to just buy 2 Bay NAS to save money I can.

Any ideas would be great.

Thanks!