Is thinking about improving one's voice to impress worshipers during night prayers considered hypocrisy (riya') that invalidates the prayer, and do seeking forgiveness (istighfar) and correcting one's intention rectify that?

Improving one's voice when reciting the Qur'an is legally (religiously) مطلوب (desirable/sought after), based on Prophetic traditions such as: "He is not of us who does not chant the Qur'an," and "Adorn the Qur'an with your voices." It is also based on the Prophet's (peace be upon him) listening to the recitations of Ibn Mas'ud and Abu Musa al-Ash'ari and being affected by them. It is preferable to improve one's voice without affectation and with a sincere intention for the sake of Allah, not for the praise of people. Improving the voice should not distract the worshiper from khushu' (devotion/humility) and tadabbur (contemplation). The fear of ostentation (riya') should motivate one towards sincerity, not towards abandoning the act itself.