I agree, better to get blockages dealt with before it become irreversible.
So yes, I think this is necessary. At this moment problems can be seen during exercising but if this is ischemia and not treated, it could soon appear during rest. I advice you not to wait too long.
The ST depression in the inferolateral leads at your top exercise level and during recovery indicates that your heart might not be getting enough oxygen.
An angiography is the logical next step to see if this really is the case and where the possible problem areas are.