Shall I do Japa of ?Om Narayana? instead of ?Om? in order to make it both Nirguna and Saguna?…

Japa of the Narayana Mantra keeps the Chaturbhuj Murti of the
Lord before my mental eyes. I, however, have been accustomed to meditate on the Murti of
Lord Krishna and am in search of a Chaturbhuj Murti of Lord Krishna with Arjun at His
feet. Please let me know how I should go on in future.

You have already created a clear mental image, momentum and force by meditating on
Lord Krishna. It is not good to change the form now. Even if you change it, the old form will
come before the mind through…