I personally wouldn't use big hi-fi speakers in a near field (desktop) setup. I found them overbearing, muddy and overall not very nice to listen to. For PC/desktop listening, and especially for your budget you'll want to chose some smaller but purposefully designed monitor speakers.
A quick look on OcUK and I'd probably be looking at this kind of thing for a low budget PC system.
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They have multiple inputs to cater for your multiple PCs and will be designed to be desktop mounted.
I have no personal experience of these speakers though but have heard other Edifier speakers which have been pretty impressive for the money. Probably a good idea to check out a few Youtube reviews to see how much of an upgrade they are over the T40s.