My router is on the other side of the hallway from me and theres nothing blocking the path except for two doors and I was wondering if i should use PCIe or USB? and if so can you give me examples of the said choice which are highly recommended. Also why do company's like netgear and asus say they can get speeds up to 450mbs but the companys that supply routers only allow like 50? By the ay my price range is sub €50
Go with USB adapter with detachable antenna (2 dBi same as PCI cards). You can place it wherever you want with usb extending cable and you'll get better signal. Your router works on 54 Mbit technology and these cards work on newer tech.
It's different standard but all these cards will work with your router.
PCIe versus USB for WiFi adapters doesn't matter a whole lot either way. Which model you get is more important than the interface that is used. Technically, one with PCIe may have an advantage with some of the fastest WiFi connections if it's also a very good model. However, in practice, the difference is not likely to be significant, let alone noticeable except for extreme situations that you won't see unless you're doing some heavy intranet transfers with proper hardware for it.