For a 2-din HU you can have a look at Pio 6050 - FH-P6050UB. Very strongly built and has lots of settings. Ipod compatible too. Another VFM option is JVC R400. Both should be around 9K. For speakers, you have 2 options. One, you get components in fronts for around 5K, and rest for wiring. Option two, you can go for 4" co-axes in fronts and 6x9 in rears and rest for wiring. If you are particular about your music, I'd suggest you to get components and later when you have some moolah you can get rear fills too.
One speaker (of any kind) can never replace 2 speakers (of any kind). Having multiple speakers at their logical positions creates a sound stage inside the vehicle. Components definitely sound lot better than co-axes so if you are the driver most of the time then go for components in the front and co-axes in the back.