No, just 1040X is not enough. You'd have to provide W-2 etc.
I'd highly recommend using a qualifying joint sponsor, using tax return transcripts instead of 1040s, making sure everybody submits proof of citizenship.
All the I-864 RFEs I've seen so far have very detailed instructions and lists of what documents USCIS expects. Send in the strongest reply, not the bare minimum or incomplete documentation, as it will lead to NOID or denial outright.