I can't see a real issue there regarding your transfer speeds.
Wireless to wired transfer with 11N will max out at about 10MB/s (sometimes I get up to 13MB/s)
Using wireless transfer with 11G to wired there will be only up to 3,5 MB/s (2MB/s also is normal) depending on the wireless chipset used.
These are speeds with only one wireless client connected. If there are more, they will share the bandwidth and slow down the wireless.
Wireless transfer is also depending on the device used. An older laptop with 11N card will most likely only transfer 6,5-9 MB/s.
These are values with a optimal connection in my home. (no other wireless networks near by and at about 3,5 m and line of sight)
I compared different cards with the same device (Thinkpad R61) and DIR-655:
- build in Atheros 5008 agn : max 10 MB/s - normal 8 MB/s
- DWA-140 (Ralink 2870) max 9,5 MB/s - normal 7 MB/s
- DWA-160 Rev A (Atheros 900x) max 13 MB/s normal 9 MB/s
- DWA-142 (Marvell Top Dog) max 9,5 MB/s normal 6 MB/s (depending on driver version)
- MSI Wind Netbook with Mini PCIe (Ralink 2860) max 8,5 MB/s - normal 5 MB/s (bad antennas cause a lot of errors and dropped packets)
Wired Gigabit transfer between DNS-323 and workstation is at about 15 MB/s with large files.
Here often the driver is the "problem". Using a Realtek 8169 Gigabit card with Win Vista drivers will slow down the speed and increase CPU usage. The same with a lot of on board devices from NVIDIA or Marvell or ...
These are only my experiences, others may reach different values depending on their environment.