The router will not affect the "sonic" quality. Since the Majik DS is configured with a Fast Ethernet port (100MB) you would get at least a router with Fast Ethernet (100MB) ports.
As for the hard drives, again it will not affect the "sonic" quality but what you're looking for is reliability. I've always used the Seagate hard drives and have never had any issues.
I have a Linn Akurate DS and what I've done is connected the Akurate DS to my router (Fast Ethernet) and I've also connected a 5-port switch (Gigabit Ethernet) to this router. To the switch, I've connected my NAS and my PC therefore when I rip my CDs to FLAC or download hi-rez FLAC files from Linn Records, the copying from my PC to NAS is a lot faster via the switch.
If your DS is in a different room than your router, you can always connect these via Power over Ethernet (PoE) adapters.
Lats, as a personal experience, stay away from D-Link, these are pretty cheap and unreliable. I've had great success with Netgear.
