Your PC will no longer to top notch once you receive it via UPS or FedEx or whomever ships it to you.
Unless you bought the most expensive of everything (i.e. $1,000 Extreme/Unlocked/BlackEdition/OMG/WTF CPU). Then it'll be less than top notch a month after you receive it.
It's all about how your system performs with what YOU are doing. If you game, and it runs all your games with good settings, is smooth and enjoyable, leave it alone.
If the new games you buy are sluggish, at medium/low settings, then you might want to consider an upgrade. There will ALWAYS be something better within 2-6 months.