I think you can use the Rocksmith cable (Real Tone cable?) as an audio interface for amp sims. Might be a way to play with effects while saving up for an amp.
If you aren't planning on playing live for an audience, you might just upgrade to a real audio interface instead of an amp.
I have the cable and have figured out that I need an ASIO4ALL driver but I am having a few hangups still. My speakers aren't too loud which is my biggest drawback.
Main issue with RTC and amp sims would be drivers. I think the only thing that would work is ASIO4All. I haven't really tried myself but my expectation is that it would have some lag to it. Something like the Fender Mustang Micro (I have this, big fan), or a NUX Mighty Plug, or the new IK iRig USB (mentioned in Guitar Geek The Week in Gear 22, seems like a crazy good deal with Amplitube and ToneX software included) would all be good options that are still useful even after OP buys an amp.