Low rates and valuations drive companies; shows confidence in the exconomy.

Busiest week for corporate issuance in five months led by Amgen.

Republican plan would raise $300 bln by overhauling the tax code.

Mention of possible euro exit exacerbates European debt crisis.

Sell-off in Italian bonds puts pressure on financial institutions.

Alabama county declares biggest-ever municipal bankruptcy.

Proposal includes equal amounts of spending cuts, tax hikes.

Rise in Italian bond yields calls into question Europe's ability to resolve crisis.