OK you have the non nav premium setup currently.
The ebay unit you linked, a few things to consider;
1- Depending on how that Chinese company has modelled the unit regarding it's dimensions, either on the OE nav unit or the OE unit you currently have, you may need to swap the upper vent panel if they have modelled the dimensions on the OE nav unit as there is a difference in front size between the OE nav and OE non nav.
2- The ebay unit you linked mentions a built in 4x45w power amplifier. All premium systems in the 2003-2007 Accord use a separate amplifier setup, so the OE premium unit 4ch output on the main power plug is LOW Line Level so if you plug a 4x45w output into the loom which still goes to the amp you will most probably fry it. Best way would be to use the RCA low line out from that Chinese unit to feed the 4ch input into the OE amp.
3- Climate controls; you will see in that Chinese unit the knobs 'D' and 'P' (Driver / Passenger) are setup for LHD, my OCD would not cope with this lol. Also will the display on this unit show the climate correctly......... always wonder about these things.
Always interesting to know peoples experiences on these Chinese units but most would say avoid them I reckon.
I did quite a bit of messing around when I converted my OE nav to OE non nav like what you have now as I hated the old crappy OE nav. Now I have a Pure DAB/BT setup feeding into the OE unit with an AUX in adapter, works ok but I plan in the future to install a single DIN fascia under the OE unit and put a proper single DIN DAB/BT/USB/Android/IPOD unit in and get that to feed the OE amp keeping the rest original.