First of all, if you like what you have then be satisfied.
I have a pair of vintage Yamaha NS-1, Elac UB5 and Monitor Audio Bronze 2 bookshelf/stand speakers sat in front of me at the moment. Despite being happy with the sound of the NS-1's, I was even happier after recapping them, but now realise that they aren't as capable in some areas as the ELAC and MA. I'm used to the laid back and easy sound of the vintage speakers so the cleaner, more forward and clinical sound of the modern speakers is a difference that I am slowly adjusting to. Is one sound better than the other, well yes and no. The soundstage and clarity of the ELAC and MA is certainly than the Yamahas but for extended periods of listening then I think the Yamahas may be a better choice. That opinion may change over time of course.
There are also modern speakers (e.g. Wharfedale Denton Anniversary) that are meant to harken back to the "old sound". I have not heard these speakers, but online reviews use such words as "polite" and "forgiving". Some modern speakers are less forgiving than others of a poor upstream component or source.
About bass. Some small, modern speakers seem give an impression of bass rather than actually pushing a lot of air to create "real" bass. Others seemingly produce a euphoric, out of body experience for some listeners - here I am thinking of the OTT "where is the sub-woofer" reviews of the UB5. For real bass some folks are going to swear by the use of a competent small speaker coupled with a separate sub-woofer.
Will a tiny modern speaker outperform a larger, older model ?
Too many variables for a definitive answer.
At the end of the day nothing can beat the use of your Mark I Mod 0 ears to be the judge of what sounds good to you. Hi-Fi is all about smoke, mirrors and subjectivity so hit the local dealers, or order some speakers online with free/cheap returns and have a listen.