Mixing Powerline Adapters

[#1]

Have been using these for a few weeks http://uk.tp-link.com/products/details/?categoryid=1658&model=TL-PA4010KIT.
Wondered if I can add one of these http://uk.tp-link.com/products/details/?categoryid=1658&model=TL-PA451 as the place I want to use it has no spare sockets?

[#2]

If you look at the specification both say
Standards and Protocols HomePlug AV, IEEE802.3, IEEE802.3u
So yes, 100% compatible.

[#3]

Excellent 

[#4]

I think I'm using an older iteration of those plugs. I have 2 x 500Mbps plugs and one 200Mbps plug on the same network and they're all able to talk to each other without any issues.

[#5]

I have two 85Mbs plugs and two 1000Mbs (claimed) plugs on the same network.
They work in pairs and can talk to each other via a common switch.

[#6]

Great things if you need em, we use a lot of these on site, and sell quite a few from the store.
However: What I noticed with powerline adapters, are sudden spikes in latency, sometimes quite big spikes, and sometimes quite regular. I've went back to cable and abusing a wireless router to turn it into an extender.
Which reminds me, I still have a bunch of powerline adapters plugged in, although only 2 of em are currently in use.
If you not bothered about occasional latency, you can't hide wires, or you live in a castle with thick walls - Powerline adapters work. For time critical applications however...

[#7]

I've never noticed latency spikes with my setup. Regularly use it to stream HD media/music across the local network.

[#8]

Been thinking about this, and wonder if the adapter plugged into the router will cope with bandwidth coming from the adapter my son's XBox AND a new adapter for his PC? Or would I be better just leaving his PC on the wifi?

[#9]

Yes it will cope.
I can run big downloads and backups simultaneously - the router will max out at a bit less than 100Mbps.
(Or possibly more if you have a Gigabit router).