I half agree with Kush. Yes you do need to identity the cause of the issue but investing in a new router and switches wouldn't be a complete waste of money if they turned out not to be the problem. You obviously want a multipurpose network which is only going to grow in the future and you need to make sure you have the appropriate network infrastructure in place to accommodate your requirements. The best way I explain it is you can give somebody superman feet and superman eyes but if you have got a spine and nerves which cant handle the super speed then you aren't going to get anywhere.
I spent the best part of £400 a couple of years ago on new routers, switches and cabling knowing that I was going to buy networked tvs, nas servers, printers etc etc and wanted to make sure everything would work properly and I wouldn't be throwing a tantrum every night. Now everyone in my house can do their own thing; I can be playing games of downloading torrents in my room, somebody can be streaming content from one of the servers to the tv downstairs, someone else can be gaming in another room and someone else can be youtubing etc and nobody would know because everything works perfectly altogether at the same time. I don't care how awesome shub2 and shubac are, I don't trust cheapo naff free stuff to handle those kind of demands which are critical to my lifestyle. I wouldn't live very long if we were unable to watch stuff like Homeland, Walking Dead, Greys and Vampire Diaries every week
You can spend £1000 on a super duper tv and £400 on a games console but none of it means anything if you cant get them to work and do what they are supposed to do.
Your speed issues might be to do with something else entirely but I would still buy a proper router and switches if you want to do the sort of things you have talked about. Freebie routers just aren't up for it.