H1B extension approved from new employer. Do I need to stamp before re-entering US?

My visa stamp was till Date Sep, 30, 2016 (stamped on my passport)

On H1B from A, while still in US, employer B hired me and currently holds my H1B

I797 for employer B is approved till Date Sep, 30, 2018 >Sep, 30, 2016 (stamped on my passport)

I will visit India in next 15 days and my return is before Sep, 30, 2016

DO i need to get stamping? Since the interview dates at the consulate I am planning to attend is available only after July?

If you plan to return prior to current visa stamp expiration date, then no new stamping is required. You can use current stamp and B’s petition to return to US.

If you want to avail stamping, then you will be eligible for dropbox and there is no need to schedule interview date for that. You can go to dropbox facility and give your documents.

Thanks Saurabh,
One more question:
When I went through the interview waiver in the us consulate site: http://chennai.usconsulate.gov/interviews-and-appointments.html

It states:
If you hold an H1-B or Individual L1-A or L1-B visa that expired within the last 12 months, you may qualify for the Interview Waiver Program. To qualify, the petitioner must be the same as on your initial visa, however, the end client need not be the same. You must present a current, valid I-129, LCA, Petitioner Letter to USCIS and pay slips showing your salary for the preceding three (3) months.

Since my petitioner changed from A to B; still I need to go through the interview process?

This is where all the updated information is: http://www.ustraveldocs.com/in/in-niv-visarenew.asp

As you can see there is no mention of change of employer. Actually it was required that employer should be same few months ago, but has since changed. Looks like Chennai consulate site was not updated.