Not sure if they come on dwarfing stocks and Paulownia has a big spread and grows to 12-15m and cuts out all the light below it (you have the 5 - 10 year heights I think) so might be a bad choice in a small garden The Albizia can grow to 12m but is quite 'lacy' so a better choice for a small garden it would look stunning with a robinia 'frisia' pseudacacia though the bright yello against the plummy tones would be very striking
http://www.johnstowng...robinia_frisiapd.aspx
seen here with a purply cotinus to give you a better idea



