LOL I wouldn't say the Netgear R9000 is "tat". Its Netgear's flagship router (costing ~ £400) which is currently the most powerful consumer router - certainly on a par with many enterprise kits wrt raw power & wifi radios. It has a 1.7ghz Alpine quadcore processor along with 1GB ram and 512mb flash memory with the latest Wave 2 wifi radios - its certainly making a difference in giving me buttery smooth Plex streams (it has a built-in Plex media server). Though once Asus release this beauty in UK, i imagine the R9000 won't be at the top of the pile anymore.
Anyway even connecting my pc directly to the SRX300 is giving me the same TBB speedtest results so the issue definitely isn't with my R9000. I suspect the SRX300 is acting as a bottleneck somewhere and I also appear to be getting a little packet loss even when my connection is idle - https://goo.gl/EnTCmk
I'm looking at the possibility of 'sniffing' out the PPPoE credentials with Wireshark on the SRX300 so i can connect the Netgear directly to the Openreach ONT. The sooner the totally locked down SRX300 is binned the better
Nope anything from Netgear is consumer grade tat, especially when the alternative is kit running Junos. Even the Netgear "enterprise" stuff is a bit ropy. I simply don't care what you think the hardware specs are it is simply not in the same class, not even by a country mile. Given Netgear's tardy history with security and timely updates, the value of proper enterprise kit that will be still getting security updates years from now, is way beyond the consumer grade tat you seem to mistakenly value so highly. Basically the hardware is irrelevant it's all about the quality of the software, how likely it is to have security problems and the likely hood that security updates will be available five years from now. On all these fronts the SX300 wins hands down, it is not even remotely close. Don't get me wrong I own Netgear stuff myself but in comparison to Juniper kit it's just not the same league.
Now if the SX300 is totally locked down even at the console then that is another matter. On the other hand you could just do password recovery on the SX300 from the serial console. Or better yet use a configuration group at the recovery prompt. I somewhat doubt that Fluidone have some special Junos version to keep out the knowledgeable.
As for performance the SX300 is rated well above a 330/30Mbps connection for routing performance unless you turn on the next gen firewall, but the Netgear does not even have one of those so the comparison is not valid. Heck a Ubiquiti Edgerouter ERlite-3 with a 500MHz CPU (admittedly with hardware acceleration) would be more than adequate. You are talking 244Kpps at 1518 packet size up to one million PPS through the fire wall at 64 byte packets, and anything from 672Mbps at 64 bytes to a full 3000Mbps at 1518 bytes packet size across all three interfaces. Basically hardware stopped being the bottleneck sometime ago now.
Also you can get multiple buttery smooth Plex streams from just a Raspberry Pi as long as it's not transcoding. If you pre-encode to H264 you are more likely to run out of devices to stream to and/or the hard disk will give out before the Pi does. However I would run (as I do) my Plex server on my NAS/file server.